7023069: G1: Introduce symmetric locking in the slow allocation path
7023151: G1: refactor the code that operates on _cur_alloc_region to be re-used for allocs by the GC threads
7018286: G1: humongous allocation attempts should take the GC locker into account
Summary: First, this change replaces the asymmetric locking scheme in the G1 slow alloc path by a summetric one. Second, it factors out the code that operates on _cur_alloc_region so that it can be re-used for allocations by the GC threads in the future.
Reviewed-by: stefank, brutisso, johnc
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1AllocRegion.cpp Wed Mar 30 10:26:59 2011 -0400
@@ -0,0 +1,208 @@
+/*
+ * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#include "precompiled.hpp"
+#include "gc_implementation/g1/g1AllocRegion.inline.hpp"
+#include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
+
+G1CollectedHeap* G1AllocRegion::_g1h = NULL;
+HeapRegion* G1AllocRegion::_dummy_region = NULL;
+
+void G1AllocRegion::setup(G1CollectedHeap* g1h, HeapRegion* dummy_region) {
+ assert(_dummy_region == NULL, "should be set once");
+ assert(dummy_region != NULL, "pre-condition");
+ assert(dummy_region->free() == 0, "pre-condition");
+
+ // Make sure that any allocation attempt on this region will fail
+ // and will not trigger any asserts.
+ assert(allocate(dummy_region, 1, false) == NULL, "should fail");
+ assert(par_allocate(dummy_region, 1, false) == NULL, "should fail");
+ assert(allocate(dummy_region, 1, true) == NULL, "should fail");
+ assert(par_allocate(dummy_region, 1, true) == NULL, "should fail");
+
+ _g1h = g1h;
+ _dummy_region = dummy_region;
+}
+
+void G1AllocRegion::fill_up_remaining_space(HeapRegion* alloc_region,
+ bool bot_updates) {
+ assert(alloc_region != NULL && alloc_region != _dummy_region,
+ "pre-condition");
+
+ // Other threads might still be trying to allocate using a CAS out
+ // of the region we are trying to retire, as they can do so without
+ // holding the lock. So, we first have to make sure that noone else
+ // can allocate out of it by doing a maximal allocation. Even if our
+ // CAS attempt fails a few times, we'll succeed sooner or later
+ // given that failed CAS attempts mean that the region is getting
+ // closed to being full.
+ size_t free_word_size = alloc_region->free() / HeapWordSize;
+
+ // This is the minimum free chunk we can turn into a dummy
+ // object. If the free space falls below this, then noone can
+ // allocate in this region anyway (all allocation requests will be
+ // of a size larger than this) so we won't have to perform the dummy
+ // allocation.
+ size_t min_word_size_to_fill = CollectedHeap::min_fill_size();
+
+ while (free_word_size >= min_word_size_to_fill) {
+ HeapWord* dummy = par_allocate(alloc_region, free_word_size, bot_updates);
+ if (dummy != NULL) {
+ // If the allocation was successful we should fill in the space.
+ CollectedHeap::fill_with_object(dummy, free_word_size);
+ alloc_region->set_pre_dummy_top(dummy);
+ break;
+ }
+
+ free_word_size = alloc_region->free() / HeapWordSize;
+ // It's also possible that someone else beats us to the
+ // allocation and they fill up the region. In that case, we can
+ // just get out of the loop.
+ }
+ assert(alloc_region->free() / HeapWordSize < min_word_size_to_fill,
+ "post-condition");
+}
+
+void G1AllocRegion::retire(bool fill_up) {
+ assert(_alloc_region != NULL, ar_ext_msg(this, "not initialized properly"));
+
+ trace("retiring");
+ HeapRegion* alloc_region = _alloc_region;
+ if (alloc_region != _dummy_region) {
+ // We never have to check whether the active region is empty or not,
+ // and potentially free it if it is, given that it's guaranteed that
+ // it will never be empty.
+ assert(!alloc_region->is_empty(),
+ ar_ext_msg(this, "the alloc region should never be empty"));
+
+ if (fill_up) {
+ fill_up_remaining_space(alloc_region, _bot_updates);
+ }
+
+ assert(alloc_region->used() >= _used_bytes_before,
+ ar_ext_msg(this, "invariant"));
+ size_t allocated_bytes = alloc_region->used() - _used_bytes_before;
+ retire_region(alloc_region, allocated_bytes);
+ _used_bytes_before = 0;
+ _alloc_region = _dummy_region;
+ }
+ trace("retired");
+}
+
+HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,
+ bool force) {
+ assert(_alloc_region == _dummy_region, ar_ext_msg(this, "pre-condition"));
+ assert(_used_bytes_before == 0, ar_ext_msg(this, "pre-condition"));
+
+ trace("attempting region allocation");
+ HeapRegion* new_alloc_region = allocate_new_region(word_size, force);
+ if (new_alloc_region != NULL) {
+ new_alloc_region->reset_pre_dummy_top();
+ // Need to do this before the allocation
+ _used_bytes_before = new_alloc_region->used();
+ HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates);
+ assert(result != NULL, ar_ext_msg(this, "the allocation should succeeded"));
+
+ OrderAccess::storestore();
+ // Note that we first perform the allocation and then we store the
+ // region in _alloc_region. This is the reason why an active region
+ // can never be empty.
+ _alloc_region = new_alloc_region;
+ trace("region allocation successful");
+ return result;
+ } else {
+ trace("region allocation failed");
+ return NULL;
+ }
+ ShouldNotReachHere();
+}
+
+void G1AllocRegion::fill_in_ext_msg(ar_ext_msg* msg, const char* message) {
+ msg->append("[%s] %s b: %s r: "PTR_FORMAT" u: "SIZE_FORMAT,
+ _name, message, BOOL_TO_STR(_bot_updates),
+ _alloc_region, _used_bytes_before);
+}
+
+void G1AllocRegion::init() {
+ trace("initializing");
+ assert(_alloc_region == NULL && _used_bytes_before == 0,
+ ar_ext_msg(this, "pre-condition"));
+ assert(_dummy_region != NULL, "should have been set");
+ _alloc_region = _dummy_region;
+ trace("initialized");
+}
+
+HeapRegion* G1AllocRegion::release() {
+ trace("releasing");
+ HeapRegion* alloc_region = _alloc_region;
+ retire(false /* fill_up */);
+ assert(_alloc_region == _dummy_region, "post-condition of retire()");
+ _alloc_region = NULL;
+ trace("released");
+ return (alloc_region == _dummy_region) ? NULL : alloc_region;
+}
+
+#if G1_ALLOC_REGION_TRACING
+void G1AllocRegion::trace(const char* str, size_t word_size, HeapWord* result) {
+ // All the calls to trace that set either just the size or the size
+ // and the result are considered part of level 2 tracing and are
+ // skipped during level 1 tracing.
+ if ((word_size == 0 && result == NULL) || (G1_ALLOC_REGION_TRACING > 1)) {
+ const size_t buffer_length = 128;
+ char hr_buffer[buffer_length];
+ char rest_buffer[buffer_length];
+
+ HeapRegion* alloc_region = _alloc_region;
+ if (alloc_region == NULL) {
+ jio_snprintf(hr_buffer, buffer_length, "NULL");
+ } else if (alloc_region == _dummy_region) {
+ jio_snprintf(hr_buffer, buffer_length, "DUMMY");
+ } else {
+ jio_snprintf(hr_buffer, buffer_length,
+ HR_FORMAT, HR_FORMAT_PARAMS(alloc_region));
+ }
+
+ if (G1_ALLOC_REGION_TRACING > 1) {
+ if (result != NULL) {
+ jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT" "PTR_FORMAT,
+ word_size, result);
+ } else if (word_size != 0) {
+ jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT, word_size);
+ } else {
+ jio_snprintf(rest_buffer, buffer_length, "");
+ }
+ } else {
+ jio_snprintf(rest_buffer, buffer_length, "");
+ }
+
+ tty->print_cr("[%s] %s : %s %s", _name, hr_buffer, str, rest_buffer);
+ }
+}
+#endif // G1_ALLOC_REGION_TRACING
+
+G1AllocRegion::G1AllocRegion(const char* name,
+ bool bot_updates)
+ : _name(name), _bot_updates(bot_updates),
+ _alloc_region(NULL), _used_bytes_before(0) { }
+
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1AllocRegion.hpp Wed Mar 30 10:26:59 2011 -0400
@@ -0,0 +1,174 @@
+/*
+ * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP
+#define SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP
+
+#include "gc_implementation/g1/heapRegion.hpp"
+
+class G1CollectedHeap;
+
+// 0 -> no tracing, 1 -> basic tracing, 2 -> basic + allocation tracing
+#define G1_ALLOC_REGION_TRACING 0
+
+class ar_ext_msg;
+
+// A class that holds a region that is active in satisfying allocation
+// requests, potentially issued in parallel. When the active region is
+// full it will be retired it replaced with a new one. The
+// implementation assumes that fast-path allocations will be lock-free
+// and a lock will need to be taken when the active region needs to be
+// replaced.
+
+class G1AllocRegion VALUE_OBJ_CLASS_SPEC {
+ friend class ar_ext_msg;
+
+private:
+ // The active allocating region we are currently allocating out
+ // of. The invariant is that if this object is initialized (i.e.,
+ // init() has been called and release() has not) then _alloc_region
+ // is either an active allocating region or the dummy region (i.e.,
+ // it can never be NULL) and this object can be used to satisfy
+ // allocation requests. If this object is not initialized
+ // (i.e. init() has not been called or release() has been called)
+ // then _alloc_region is NULL and this object should not be used to
+ // satisfy allocation requests (it was done this way to force the
+ // correct use of init() and release()).
+ HeapRegion* _alloc_region;
+
+ // When we set up a new active region we save its used bytes in this
+ // field so that, when we retire it, we can calculate how much space
+ // we allocated in it.
+ size_t _used_bytes_before;
+
+ // Specifies whether the allocate calls will do BOT updates or not.
+ bool _bot_updates;
+
+ // Useful for debugging and tracing.
+ const char* _name;
+
+ // A dummy region (i.e., it's been allocated specially for this
+ // purpose and it is not part of the heap) that is full (i.e., top()
+ // == end()). When we don't have a valid active region we make
+ // _alloc_region point to this. This allows us to skip checking
+ // whether the _alloc_region is NULL or not.
+ static HeapRegion* _dummy_region;
+
+ // Some of the methods below take a bot_updates parameter. Its value
+ // should be the same as the _bot_updates field. The idea is that
+ // the parameter will be a constant for a particular alloc region
+ // and, given that these methods will be hopefully inlined, the
+ // compiler should compile out the test.
+
+ // Perform a non-MT-safe allocation out of the given region.
+ static inline HeapWord* allocate(HeapRegion* alloc_region,
+ size_t word_size,
+ bool bot_updates);
+
+ // Perform a MT-safe allocation out of the given region.
+ static inline HeapWord* par_allocate(HeapRegion* alloc_region,
+ size_t word_size,
+ bool bot_updates);
+
+ // Ensure that the region passed as a parameter has been filled up
+ // so that noone else can allocate out of it any more.
+ static void fill_up_remaining_space(HeapRegion* alloc_region,
+ bool bot_updates);
+
+ // Retire the active allocating region. If fill_up is true then make
+ // sure that the region is full before we retire it so that noone
+ // else can allocate out of it.
+ void retire(bool fill_up);
+
+ // Allocate a new active region and use it to perform a word_size
+ // allocation. The force parameter will be passed on to
+ // G1CollectedHeap::allocate_new_alloc_region() and tells it to try
+ // to allocate a new region even if the max has been reached.
+ HeapWord* new_alloc_region_and_allocate(size_t word_size, bool force);
+
+ void fill_in_ext_msg(ar_ext_msg* msg, const char* message);
+
+protected:
+ // For convenience as subclasses use it.
+ static G1CollectedHeap* _g1h;
+
+ virtual HeapRegion* allocate_new_region(size_t word_size, bool force) = 0;
+ virtual void retire_region(HeapRegion* alloc_region,
+ size_t allocated_bytes) = 0;
+
+ G1AllocRegion(const char* name, bool bot_updates);
+
+public:
+ static void setup(G1CollectedHeap* g1h, HeapRegion* dummy_region);
+
+ HeapRegion* get() const {
+ // Make sure that the dummy region does not escape this class.
+ return (_alloc_region == _dummy_region) ? NULL : _alloc_region;
+ }
+
+ // The following two are the building blocks for the allocation method.
+
+ // First-level allocation: Should be called without holding a
+ // lock. It will try to allocate lock-free out of the active region,
+ // or return NULL if it was unable to.
+ inline HeapWord* attempt_allocation(size_t word_size, bool bot_updates);
+
+ // Second-level allocation: Should be called while holding a
+ // lock. It will try to first allocate lock-free out of the active
+ // region or, if it's unable to, it will try to replace the active
+ // alloc region with a new one. We require that the caller takes the
+ // appropriate lock before calling this so that it is easier to make
+ // it conform to its locking protocol.
+ inline HeapWord* attempt_allocation_locked(size_t word_size,
+ bool bot_updates);
+
+ // Should be called to allocate a new region even if the max of this
+ // type of regions has been reached. Should only be called if other
+ // allocation attempts have failed and we are not holding a valid
+ // active region.
+ inline HeapWord* attempt_allocation_force(size_t word_size,
+ bool bot_updates);
+
+ // Should be called before we start using this object.
+ void init();
+
+ // Should be called when we want to release the active region which
+ // is returned after it's been retired.
+ HeapRegion* release();
+
+#if G1_ALLOC_REGION_TRACING
+ void trace(const char* str, size_t word_size = 0, HeapWord* result = NULL);
+#else // G1_ALLOC_REGION_TRACING
+ void trace(const char* str, size_t word_size = 0, HeapWord* result = NULL) { }
+#endif // G1_ALLOC_REGION_TRACING
+};
+
+class ar_ext_msg : public err_msg {
+public:
+ ar_ext_msg(G1AllocRegion* alloc_region, const char *message) : err_msg("") {
+ alloc_region->fill_in_ext_msg(this, message);
+ }
+};
+
+#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_HPP
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1AllocRegion.inline.hpp Wed Mar 30 10:26:59 2011 -0400
@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ *
+ */
+
+#ifndef SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_INLINE_HPP
+#define SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_INLINE_HPP
+
+#include "gc_implementation/g1/g1AllocRegion.hpp"
+
+inline HeapWord* G1AllocRegion::allocate(HeapRegion* alloc_region,
+ size_t word_size,
+ bool bot_updates) {
+ assert(alloc_region != NULL, err_msg("pre-condition"));
+
+ if (!bot_updates) {
+ return alloc_region->allocate_no_bot_updates(word_size);
+ } else {
+ return alloc_region->allocate(word_size);
+ }
+}
+
+inline HeapWord* G1AllocRegion::par_allocate(HeapRegion* alloc_region,
+ size_t word_size,
+ bool bot_updates) {
+ assert(alloc_region != NULL, err_msg("pre-condition"));
+ assert(!alloc_region->is_empty(), err_msg("pre-condition"));
+
+ if (!bot_updates) {
+ return alloc_region->par_allocate_no_bot_updates(word_size);
+ } else {
+ return alloc_region->par_allocate(word_size);
+ }
+}
+
+inline HeapWord* G1AllocRegion::attempt_allocation(size_t word_size,
+ bool bot_updates) {
+ assert(bot_updates == _bot_updates, ar_ext_msg(this, "pre-condition"));
+
+ HeapRegion* alloc_region = _alloc_region;
+ assert(alloc_region != NULL, ar_ext_msg(this, "not initialized properly"));
+
+ HeapWord* result = par_allocate(alloc_region, word_size, bot_updates);
+ if (result != NULL) {
+ trace("alloc", word_size, result);
+ return result;
+ }
+ trace("alloc failed", word_size);
+ return NULL;
+}
+
+inline HeapWord* G1AllocRegion::attempt_allocation_locked(size_t word_size,
+ bool bot_updates) {
+ // First we have to tedo the allocation, assuming we're holding the
+ // appropriate lock, in case another thread changed the region while
+ // we were waiting to get the lock.
+ HeapWord* result = attempt_allocation(word_size, bot_updates);
+ if (result != NULL) {
+ return result;
+ }
+
+ retire(true /* fill_up */);
+ result = new_alloc_region_and_allocate(word_size, false /* force */);
+ if (result != NULL) {
+ trace("alloc locked (second attempt)", word_size, result);
+ return result;
+ }
+ trace("alloc locked failed", word_size);
+ return NULL;
+}
+
+inline HeapWord* G1AllocRegion::attempt_allocation_force(size_t word_size,
+ bool bot_updates) {
+ assert(bot_updates == _bot_updates, ar_ext_msg(this, "pre-condition"));
+ assert(_alloc_region != NULL, ar_ext_msg(this, "not initialized properly"));
+
+ trace("forcing alloc");
+ HeapWord* result = new_alloc_region_and_allocate(word_size, true /* force */);
+ if (result != NULL) {
+ trace("alloc forced", word_size, result);
+ return result;
+ }
+ trace("alloc forced failed", word_size);
+ return NULL;
+}
+
+#endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1ALLOCREGION_INLINE_HPP
--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp Tue Mar 29 22:36:16 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp Wed Mar 30 10:26:59 2011 -0400
@@ -28,6 +28,7 @@
#include "gc_implementation/g1/concurrentG1Refine.hpp"
#include "gc_implementation/g1/concurrentG1RefineThread.hpp"
#include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
+#include "gc_implementation/g1/g1AllocRegion.inline.hpp"
#include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
#include "gc_implementation/g1/g1CollectorPolicy.hpp"
#include "gc_implementation/g1/g1MarkSweep.hpp"
@@ -517,8 +518,7 @@
return NULL;
}
-HeapRegion* G1CollectedHeap::new_region_work(size_t word_size,
- bool do_expand) {
+HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
assert(!isHumongous(word_size) ||
word_size <= (size_t) HeapRegion::GrainWords,
"the only time we use this to allocate a humongous region is "
@@ -566,7 +566,7 @@
size_t word_size) {
HeapRegion* alloc_region = NULL;
if (_gc_alloc_region_counts[purpose] < g1_policy()->max_regions(purpose)) {
- alloc_region = new_region_work(word_size, true /* do_expand */);
+ alloc_region = new_region(word_size, true /* do_expand */);
if (purpose == GCAllocForSurvived && alloc_region != NULL) {
alloc_region->set_survivor();
}
@@ -587,7 +587,7 @@
// Only one region to allocate, no need to go through the slower
// path. The caller will attempt the expasion if this fails, so
// let's not try to expand here too.
- HeapRegion* hr = new_region_work(word_size, false /* do_expand */);
+ HeapRegion* hr = new_region(word_size, false /* do_expand */);
if (hr != NULL) {
first = hr->hrs_index();
} else {
@@ -788,407 +788,12 @@
return result;
}
-void
-G1CollectedHeap::retire_cur_alloc_region(HeapRegion* cur_alloc_region) {
- // Other threads might still be trying to allocate using CASes out
- // of the region we are retiring, as they can do so without holding
- // the Heap_lock. So we first have to make sure that noone else can
- // allocate in it by doing a maximal allocation. Even if our CAS
- // attempt fails a few times, we'll succeed sooner or later given
- // that a failed CAS attempt mean that the region is getting closed
- // to being full (someone else succeeded in allocating into it).
- size_t free_word_size = cur_alloc_region->free() / HeapWordSize;
-
- // This is the minimum free chunk we can turn into a dummy
- // object. If the free space falls below this, then noone can
- // allocate in this region anyway (all allocation requests will be
- // of a size larger than this) so we won't have to perform the dummy
- // allocation.
- size_t min_word_size_to_fill = CollectedHeap::min_fill_size();
-
- while (free_word_size >= min_word_size_to_fill) {
- HeapWord* dummy =
- cur_alloc_region->par_allocate_no_bot_updates(free_word_size);
- if (dummy != NULL) {
- // If the allocation was successful we should fill in the space.
- CollectedHeap::fill_with_object(dummy, free_word_size);
- break;
- }
-
- free_word_size = cur_alloc_region->free() / HeapWordSize;
- // It's also possible that someone else beats us to the
- // allocation and they fill up the region. In that case, we can
- // just get out of the loop
- }
- assert(cur_alloc_region->free() / HeapWordSize < min_word_size_to_fill,
- "sanity");
-
- retire_cur_alloc_region_common(cur_alloc_region);
- assert(_cur_alloc_region == NULL, "post-condition");
-}
-
-// See the comment in the .hpp file about the locking protocol and
-// assumptions of this method (and other related ones).
-HeapWord*
-G1CollectedHeap::replace_cur_alloc_region_and_allocate(size_t word_size,
- bool at_safepoint,
- bool do_dirtying,
- bool can_expand) {
- assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
- assert(_cur_alloc_region == NULL,
- "replace_cur_alloc_region_and_allocate() should only be called "
- "after retiring the previous current alloc region");
- assert(SafepointSynchronize::is_at_safepoint() == at_safepoint,
- "at_safepoint and is_at_safepoint() should be a tautology");
- assert(!can_expand || g1_policy()->can_expand_young_list(),
- "we should not call this method with can_expand == true if "
- "we are not allowed to expand the young gen");
-
- if (can_expand || !g1_policy()->is_young_list_full()) {
- HeapRegion* new_cur_alloc_region = new_alloc_region(word_size);
- if (new_cur_alloc_region != NULL) {
- assert(new_cur_alloc_region->is_empty(),
- "the newly-allocated region should be empty, "
- "as right now we only allocate new regions out of the free list");
- g1_policy()->update_region_num(true /* next_is_young */);
- set_region_short_lived_locked(new_cur_alloc_region);
-
- assert(!new_cur_alloc_region->isHumongous(),
- "Catch a regression of this bug.");
-
- // We need to ensure that the stores to _cur_alloc_region and,
- // subsequently, to top do not float above the setting of the
- // young type.
- OrderAccess::storestore();
-
- // Now, perform the allocation out of the region we just
- // allocated. Note that noone else can access that region at
- // this point (as _cur_alloc_region has not been updated yet),
- // so we can just go ahead and do the allocation without any
- // atomics (and we expect this allocation attempt to
- // suceeded). Given that other threads can attempt an allocation
- // with a CAS and without needing the Heap_lock, if we assigned
- // the new region to _cur_alloc_region before first allocating
- // into it other threads might have filled up the new region
- // before we got a chance to do the allocation ourselves. In
- // that case, we would have needed to retire the region, grab a
- // new one, and go through all this again. Allocating out of the
- // new region before assigning it to _cur_alloc_region avoids
- // all this.
- HeapWord* result =
- new_cur_alloc_region->allocate_no_bot_updates(word_size);
- assert(result != NULL, "we just allocate out of an empty region "
- "so allocation should have been successful");
- assert(is_in(result), "result should be in the heap");
-
- // Now make sure that the store to _cur_alloc_region does not
- // float above the store to top.
- OrderAccess::storestore();
- _cur_alloc_region = new_cur_alloc_region;
-
- if (!at_safepoint) {
- Heap_lock->unlock();
- }
-
- // do the dirtying, if necessary, after we release the Heap_lock
- if (do_dirtying) {
- dirty_young_block(result, word_size);
- }
- return result;
- }
- }
-
- assert(_cur_alloc_region == NULL, "we failed to allocate a new current "
- "alloc region, it should still be NULL");
- assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
- return NULL;
-}
-
-// See the comment in the .hpp file about the locking protocol and
-// assumptions of this method (and other related ones).
-HeapWord*
-G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
- assert_heap_locked_and_not_at_safepoint();
- assert(!isHumongous(word_size), "attempt_allocation_slow() should not be "
- "used for humongous allocations");
-
- // We should only reach here when we were unable to allocate
- // otherwise. So, we should have not active current alloc region.
- assert(_cur_alloc_region == NULL, "current alloc region should be NULL");
-
- // We will loop while succeeded is false, which means that we tried
- // to do a collection, but the VM op did not succeed. So, when we
- // exit the loop, either one of the allocation attempts was
- // successful, or we succeeded in doing the VM op but which was
- // unable to allocate after the collection.
- for (int try_count = 1; /* we'll return or break */; try_count += 1) {
- bool succeeded = true;
-
- // Every time we go round the loop we should be holding the Heap_lock.
- assert_heap_locked();
-
- if (GC_locker::is_active_and_needs_gc()) {
- // We are locked out of GC because of the GC locker. We can
- // allocate a new region only if we can expand the young gen.
-
- if (g1_policy()->can_expand_young_list()) {
- // Yes, we are allowed to expand the young gen. Let's try to
- // allocate a new current alloc region.
- HeapWord* result =
- replace_cur_alloc_region_and_allocate(word_size,
- false, /* at_safepoint */
- true, /* do_dirtying */
- true /* can_expand */);
- if (result != NULL) {
- assert_heap_not_locked();
- return result;
- }
- }
- // We could not expand the young gen further (or we could but we
- // failed to allocate a new region). We'll stall until the GC
- // locker forces a GC.
-
- // If this thread is not in a jni critical section, we stall
- // the requestor until the critical section has cleared and
- // GC allowed. When the critical section clears, a GC is
- // initiated by the last thread exiting the critical section; so
- // we retry the allocation sequence from the beginning of the loop,
- // rather than causing more, now probably unnecessary, GC attempts.
- JavaThread* jthr = JavaThread::current();
- assert(jthr != NULL, "sanity");
- if (jthr->in_critical()) {
- if (CheckJNICalls) {
- fatal("Possible deadlock due to allocating while"
- " in jni critical section");
- }
- // We are returning NULL so the protocol is that we're still
- // holding the Heap_lock.
- assert_heap_locked();
- return NULL;
- }
-
- Heap_lock->unlock();
- GC_locker::stall_until_clear();
-
- // No need to relock the Heap_lock. We'll fall off to the code
- // below the else-statement which assumes that we are not
- // holding the Heap_lock.
- } else {
- // We are not locked out. So, let's try to do a GC. The VM op
- // will retry the allocation before it completes.
-
- // Read the GC count while holding the Heap_lock
- unsigned int gc_count_before = SharedHeap::heap()->total_collections();
-
- Heap_lock->unlock();
-
- HeapWord* result =
- do_collection_pause(word_size, gc_count_before, &succeeded);
- assert_heap_not_locked();
- if (result != NULL) {
- assert(succeeded, "the VM op should have succeeded");
-
- // Allocations that take place on VM operations do not do any
- // card dirtying and we have to do it here.
- dirty_young_block(result, word_size);
- return result;
- }
- }
-
- // Both paths that get us here from above unlock the Heap_lock.
- assert_heap_not_locked();
-
- // We can reach here when we were unsuccessful in doing a GC,
- // because another thread beat us to it, or because we were locked
- // out of GC due to the GC locker. In either case a new alloc
- // region might be available so we will retry the allocation.
- HeapWord* result = attempt_allocation(word_size);
- if (result != NULL) {
- assert_heap_not_locked();
- return result;
- }
-
- // So far our attempts to allocate failed. The only time we'll go
- // around the loop and try again is if we tried to do a GC and the
- // VM op that we tried to schedule was not successful because
- // another thread beat us to it. If that happened it's possible
- // that by the time we grabbed the Heap_lock again and tried to
- // allocate other threads filled up the young generation, which
- // means that the allocation attempt after the GC also failed. So,
- // it's worth trying to schedule another GC pause.
- if (succeeded) {
- break;
- }
-
- // Give a warning if we seem to be looping forever.
- if ((QueuedAllocationWarningCount > 0) &&
- (try_count % QueuedAllocationWarningCount == 0)) {
- warning("G1CollectedHeap::attempt_allocation_slow() "
- "retries %d times", try_count);
- }
- }
-
- assert_heap_locked();
- return NULL;
-}
-
-// See the comment in the .hpp file about the locking protocol and
-// assumptions of this method (and other related ones).
-HeapWord*
-G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
- bool at_safepoint) {
- // This is the method that will allocate a humongous object. All
- // allocation paths that attempt to allocate a humongous object
- // should eventually reach here. Currently, the only paths are from
- // mem_allocate() and attempt_allocation_at_safepoint().
- assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
- assert(isHumongous(word_size), "attempt_allocation_humongous() "
- "should only be used for humongous allocations");
- assert(SafepointSynchronize::is_at_safepoint() == at_safepoint,
- "at_safepoint and is_at_safepoint() should be a tautology");
-
- HeapWord* result = NULL;
-
- // We will loop while succeeded is false, which means that we tried
- // to do a collection, but the VM op did not succeed. So, when we
- // exit the loop, either one of the allocation attempts was
- // successful, or we succeeded in doing the VM op but which was
- // unable to allocate after the collection.
- for (int try_count = 1; /* we'll return or break */; try_count += 1) {
- bool succeeded = true;
-
- // Given that humongous objects are not allocated in young
- // regions, we'll first try to do the allocation without doing a
- // collection hoping that there's enough space in the heap.
- result = humongous_obj_allocate(word_size);
- assert(_cur_alloc_region == NULL || !_cur_alloc_region->isHumongous(),
- "catch a regression of this bug.");
- if (result != NULL) {
- if (!at_safepoint) {
- // If we're not at a safepoint, unlock the Heap_lock.
- Heap_lock->unlock();
- }
- return result;
- }
-
- // If we failed to allocate the humongous object, we should try to
- // do a collection pause (if we're allowed) in case it reclaims
- // enough space for the allocation to succeed after the pause.
- if (!at_safepoint) {
- // Read the GC count while holding the Heap_lock
- unsigned int gc_count_before = SharedHeap::heap()->total_collections();
-
- // If we're allowed to do a collection we're not at a
- // safepoint, so it is safe to unlock the Heap_lock.
- Heap_lock->unlock();
-
- result = do_collection_pause(word_size, gc_count_before, &succeeded);
- assert_heap_not_locked();
- if (result != NULL) {
- assert(succeeded, "the VM op should have succeeded");
- return result;
- }
-
- // If we get here, the VM operation either did not succeed
- // (i.e., another thread beat us to it) or it succeeded but
- // failed to allocate the object.
-
- // If we're allowed to do a collection we're not at a
- // safepoint, so it is safe to lock the Heap_lock.
- Heap_lock->lock();
- }
-
- assert(result == NULL, "otherwise we should have exited the loop earlier");
-
- // So far our attempts to allocate failed. The only time we'll go
- // around the loop and try again is if we tried to do a GC and the
- // VM op that we tried to schedule was not successful because
- // another thread beat us to it. That way it's possible that some
- // space was freed up by the thread that successfully scheduled a
- // GC. So it's worth trying to allocate again.
- if (succeeded) {
- break;
- }
-
- // Give a warning if we seem to be looping forever.
- if ((QueuedAllocationWarningCount > 0) &&
- (try_count % QueuedAllocationWarningCount == 0)) {
- warning("G1CollectedHeap::attempt_allocation_humongous "
- "retries %d times", try_count);
- }
- }
-
- assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
- return NULL;
-}
-
-HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
- bool expect_null_cur_alloc_region) {
- assert_at_safepoint(true /* should_be_vm_thread */);
- assert(_cur_alloc_region == NULL || !expect_null_cur_alloc_region,
- err_msg("the current alloc region was unexpectedly found "
- "to be non-NULL, cur alloc region: "PTR_FORMAT" "
- "expect_null_cur_alloc_region: %d word_size: "SIZE_FORMAT,
- _cur_alloc_region, expect_null_cur_alloc_region, word_size));
-
- if (!isHumongous(word_size)) {
- if (!expect_null_cur_alloc_region) {
- HeapRegion* cur_alloc_region = _cur_alloc_region;
- if (cur_alloc_region != NULL) {
- // We are at a safepoint so no reason to use the MT-safe version.
- HeapWord* result = cur_alloc_region->allocate_no_bot_updates(word_size);
- if (result != NULL) {
- assert(is_in(result), "result should be in the heap");
-
- // We will not do any dirtying here. This is guaranteed to be
- // called during a safepoint and the thread that scheduled the
- // pause will do the dirtying if we return a non-NULL result.
- return result;
- }
-
- retire_cur_alloc_region_common(cur_alloc_region);
- }
- }
-
- assert(_cur_alloc_region == NULL,
- "at this point we should have no cur alloc region");
- return replace_cur_alloc_region_and_allocate(word_size,
- true, /* at_safepoint */
- false /* do_dirtying */,
- false /* can_expand */);
- } else {
- return attempt_allocation_humongous(word_size,
- true /* at_safepoint */);
- }
-
- ShouldNotReachHere();
-}
-
HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
assert_heap_not_locked_and_not_at_safepoint();
- assert(!isHumongous(word_size), "we do not allow TLABs of humongous size");
-
- // First attempt: Try allocating out of the current alloc region
- // using a CAS. If that fails, take the Heap_lock and retry the
- // allocation, potentially replacing the current alloc region.
- HeapWord* result = attempt_allocation(word_size);
- if (result != NULL) {
- assert_heap_not_locked();
- return result;
- }
-
- // Second attempt: Go to the slower path where we might try to
- // schedule a collection.
- result = attempt_allocation_slow(word_size);
- if (result != NULL) {
- assert_heap_not_locked();
- return result;
- }
-
- assert_heap_locked();
- // Need to unlock the Heap_lock before returning.
- Heap_lock->unlock();
- return NULL;
+ assert(!isHumongous(word_size), "we do not allow humongous TLABs");
+
+ unsigned int dummy_gc_count_before;
+ return attempt_allocation(word_size, &dummy_gc_count_before);
}
HeapWord*
@@ -1200,48 +805,18 @@
assert(!is_tlab, "mem_allocate() this should not be called directly "
"to allocate TLABs");
- // Loop until the allocation is satisified,
- // or unsatisfied after GC.
+ // Loop until the allocation is satisified, or unsatisfied after GC.
for (int try_count = 1; /* we'll return */; try_count += 1) {
unsigned int gc_count_before;
- {
- if (!isHumongous(word_size)) {
- // First attempt: Try allocating out of the current alloc region
- // using a CAS. If that fails, take the Heap_lock and retry the
- // allocation, potentially replacing the current alloc region.
- HeapWord* result = attempt_allocation(word_size);
- if (result != NULL) {
- assert_heap_not_locked();
- return result;
- }
-
- assert_heap_locked();
-
- // Second attempt: Go to the slower path where we might try to
- // schedule a collection.
- result = attempt_allocation_slow(word_size);
- if (result != NULL) {
- assert_heap_not_locked();
- return result;
- }
- } else {
- // attempt_allocation_humongous() requires the Heap_lock to be held.
- Heap_lock->lock();
-
- HeapWord* result = attempt_allocation_humongous(word_size,
- false /* at_safepoint */);
- if (result != NULL) {
- assert_heap_not_locked();
- return result;
- }
- }
-
- assert_heap_locked();
- // Read the gc count while the heap lock is held.
- gc_count_before = SharedHeap::heap()->total_collections();
-
- // Release the Heap_lock before attempting the collection.
- Heap_lock->unlock();
+
+ HeapWord* result = NULL;
+ if (!isHumongous(word_size)) {
+ result = attempt_allocation(word_size, &gc_count_before);
+ } else {
+ result = attempt_allocation_humongous(word_size, &gc_count_before);
+ }
+ if (result != NULL) {
+ return result;
}
// Create the garbage collection operation...
@@ -1249,7 +824,6 @@
// ...and get the VM thread to execute it.
VMThread::execute(&op);
- assert_heap_not_locked();
if (op.prologue_succeeded() && op.pause_succeeded()) {
// If the operation was successful we'll return the result even
// if it is NULL. If the allocation attempt failed immediately
@@ -1275,21 +849,207 @@
}
ShouldNotReachHere();
+ return NULL;
}
-void G1CollectedHeap::abandon_cur_alloc_region() {
+HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
+ unsigned int *gc_count_before_ret) {
+ // Make sure you read the note in attempt_allocation_humongous().
+
+ assert_heap_not_locked_and_not_at_safepoint();
+ assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
+ "be called for humongous allocation requests");
+
+ // We should only get here after the first-level allocation attempt
+ // (attempt_allocation()) failed to allocate.
+
+ // We will loop until a) we manage to successfully perform the
+ // allocation or b) we successfully schedule a collection which
+ // fails to perform the allocation. b) is the only case when we'll
+ // return NULL.
+ HeapWord* result = NULL;
+ for (int try_count = 1; /* we'll return */; try_count += 1) {
+ bool should_try_gc;
+ unsigned int gc_count_before;
+
+ {
+ MutexLockerEx x(Heap_lock);
+
+ result = _mutator_alloc_region.attempt_allocation_locked(word_size,
+ false /* bot_updates */);
+ if (result != NULL) {
+ return result;
+ }
+
+ // If we reach here, attempt_allocation_locked() above failed to
+ // allocate a new region. So the mutator alloc region should be NULL.
+ assert(_mutator_alloc_region.get() == NULL, "only way to get here");
+
+ if (GC_locker::is_active_and_needs_gc()) {
+ if (g1_policy()->can_expand_young_list()) {
+ result = _mutator_alloc_region.attempt_allocation_force(word_size,
+ false /* bot_updates */);
+ if (result != NULL) {
+ return result;
+ }
+ }
+ should_try_gc = false;
+ } else {
+ // Read the GC count while still holding the Heap_lock.
+ gc_count_before = SharedHeap::heap()->total_collections();
+ should_try_gc = true;
+ }
+ }
+
+ if (should_try_gc) {
+ bool succeeded;
+ result = do_collection_pause(word_size, gc_count_before, &succeeded);
+ if (result != NULL) {
+ assert(succeeded, "only way to get back a non-NULL result");
+ return result;
+ }
+
+ if (succeeded) {
+ // If we get here we successfully scheduled a collection which
+ // failed to allocate. No point in trying to allocate
+ // further. We'll just return NULL.
+ MutexLockerEx x(Heap_lock);
+ *gc_count_before_ret = SharedHeap::heap()->total_collections();
+ return NULL;
+ }
+ } else {
+ GC_locker::stall_until_clear();
+ }
+
+ // We can reach here if we were unsuccessul in scheduling a
+ // collection (because another thread beat us to it) or if we were
+ // stalled due to the GC locker. In either can we should retry the
+ // allocation attempt in case another thread successfully
+ // performed a collection and reclaimed enough space. We do the
+ // first attempt (without holding the Heap_lock) here and the
+ // follow-on attempt will be at the start of the next loop
+ // iteration (after taking the Heap_lock).
+ result = _mutator_alloc_region.attempt_allocation(word_size,
+ false /* bot_updates */);
+ if (result != NULL ){
+ return result;
+ }
+
+ // Give a warning if we seem to be looping forever.
+ if ((QueuedAllocationWarningCount > 0) &&
+ (try_count % QueuedAllocationWarningCount == 0)) {
+ warning("G1CollectedHeap::attempt_allocation_slow() "
+ "retries %d times", try_count);
+ }
+ }
+
+ ShouldNotReachHere();
+ return NULL;
+}
+
+HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
+ unsigned int * gc_count_before_ret) {
+ // The structure of this method has a lot of similarities to
+ // attempt_allocation_slow(). The reason these two were not merged
+ // into a single one is that such a method would require several "if
+ // allocation is not humongous do this, otherwise do that"
+ // conditional paths which would obscure its flow. In fact, an early
+ // version of this code did use a unified method which was harder to
+ // follow and, as a result, it had subtle bugs that were hard to
+ // track down. So keeping these two methods separate allows each to
+ // be more readable. It will be good to keep these two in sync as
+ // much as possible.
+
+ assert_heap_not_locked_and_not_at_safepoint();
+ assert(isHumongous(word_size), "attempt_allocation_humongous() "
+ "should only be called for humongous allocations");
+
+ // We will loop until a) we manage to successfully perform the
+ // allocation or b) we successfully schedule a collection which
+ // fails to perform the allocation. b) is the only case when we'll
+ // return NULL.
+ HeapWord* result = NULL;
+ for (int try_count = 1; /* we'll return */; try_count += 1) {
+ bool should_try_gc;
+ unsigned int gc_count_before;
+
+ {
+ MutexLockerEx x(Heap_lock);
+
+ // Given that humongous objects are not allocated in young
+ // regions, we'll first try to do the allocation without doing a
+ // collection hoping that there's enough space in the heap.
+ result = humongous_obj_allocate(word_size);
+ if (result != NULL) {
+ return result;
+ }
+
+ if (GC_locker::is_active_and_needs_gc()) {
+ should_try_gc = false;
+ } else {
+ // Read the GC count while still holding the Heap_lock.
+ gc_count_before = SharedHeap::heap()->total_collections();
+ should_try_gc = true;
+ }
+ }
+
+ if (should_try_gc) {
+ // If we failed to allocate the humongous object, we should try to
+ // do a collection pause (if we're allowed) in case it reclaims
+ // enough space for the allocation to succeed after the pause.
+
+ bool succeeded;
+ result = do_collection_pause(word_size, gc_count_before, &succeeded);
+ if (result != NULL) {
+ assert(succeeded, "only way to get back a non-NULL result");
+ return result;
+ }
+
+ if (succeeded) {
+ // If we get here we successfully scheduled a collection which
+ // failed to allocate. No point in trying to allocate
+ // further. We'll just return NULL.
+ MutexLockerEx x(Heap_lock);
+ *gc_count_before_ret = SharedHeap::heap()->total_collections();
+ return NULL;
+ }
+ } else {
+ GC_locker::stall_until_clear();
+ }
+
+ // We can reach here if we were unsuccessul in scheduling a
+ // collection (because another thread beat us to it) or if we were
+ // stalled due to the GC locker. In either can we should retry the
+ // allocation attempt in case another thread successfully
+ // performed a collection and reclaimed enough space. Give a
+ // warning if we seem to be looping forever.
+
+ if ((QueuedAllocationWarningCount > 0) &&
+ (try_count % QueuedAllocationWarningCount == 0)) {
+ warning("G1CollectedHeap::attempt_allocation_humongous() "
+ "retries %d times", try_count);
+ }
+ }
+
+ ShouldNotReachHere();
+ return NULL;
+}
+
+HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
+ bool expect_null_mutator_alloc_region) {
assert_at_safepoint(true /* should_be_vm_thread */);
-
- HeapRegion* cur_alloc_region = _cur_alloc_region;
- if (cur_alloc_region != NULL) {
- assert(!cur_alloc_region->is_empty(),
- "the current alloc region can never be empty");
- assert(cur_alloc_region->is_young(),
- "the current alloc region should be young");
-
- retire_cur_alloc_region_common(cur_alloc_region);
- }
- assert(_cur_alloc_region == NULL, "post-condition");
+ assert(_mutator_alloc_region.get() == NULL ||
+ !expect_null_mutator_alloc_region,
+ "the current alloc region was unexpectedly found to be non-NULL");
+
+ if (!isHumongous(word_size)) {
+ return _mutator_alloc_region.attempt_allocation_locked(word_size,
+ false /* bot_updates */);
+ } else {
+ return humongous_obj_allocate(word_size);
+ }
+
+ ShouldNotReachHere();
}
void G1CollectedHeap::abandon_gc_alloc_regions() {
@@ -1417,8 +1177,8 @@
if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
+ gclog_or_tty->print(" VerifyBeforeGC:");
prepare_for_verify();
- gclog_or_tty->print(" VerifyBeforeGC:");
Universe::verify(true);
}
@@ -1439,9 +1199,8 @@
concurrent_mark()->abort();
// Make sure we'll choose a new allocation region afterwards.
- abandon_cur_alloc_region();
+ release_mutator_alloc_region();
abandon_gc_alloc_regions();
- assert(_cur_alloc_region == NULL, "Invariant.");
g1_rem_set()->cleanupHRRS();
tear_down_region_lists();
@@ -1547,6 +1306,8 @@
// evacuation pause.
clear_cset_fast_test();
+ init_mutator_alloc_region();
+
double end = os::elapsedTime();
g1_policy()->record_full_collection_end();
@@ -1720,8 +1481,9 @@
*succeeded = true;
// Let's attempt the allocation first.
- HeapWord* result = attempt_allocation_at_safepoint(word_size,
- false /* expect_null_cur_alloc_region */);
+ HeapWord* result =
+ attempt_allocation_at_safepoint(word_size,
+ false /* expect_null_mutator_alloc_region */);
if (result != NULL) {
assert(*succeeded, "sanity");
return result;
@@ -1748,7 +1510,7 @@
// Retry the allocation
result = attempt_allocation_at_safepoint(word_size,
- true /* expect_null_cur_alloc_region */);
+ true /* expect_null_mutator_alloc_region */);
if (result != NULL) {
assert(*succeeded, "sanity");
return result;
@@ -1765,7 +1527,7 @@
// Retry the allocation once more
result = attempt_allocation_at_safepoint(word_size,
- true /* expect_null_cur_alloc_region */);
+ true /* expect_null_mutator_alloc_region */);
if (result != NULL) {
assert(*succeeded, "sanity");
return result;
@@ -1796,7 +1558,7 @@
if (expand(expand_bytes)) {
verify_region_sets_optional();
return attempt_allocation_at_safepoint(word_size,
- false /* expect_null_cur_alloc_region */);
+ false /* expect_null_mutator_alloc_region */);
}
return NULL;
}
@@ -1940,7 +1702,6 @@
_evac_failure_scan_stack(NULL) ,
_mark_in_progress(false),
_cg1r(NULL), _summary_bytes_used(0),
- _cur_alloc_region(NULL),
_refine_cte_cl(NULL),
_full_collection(false),
_free_list("Master Free List"),
@@ -2099,7 +1860,6 @@
_g1_max_committed = _g1_committed;
_hrs = new HeapRegionSeq(_expansion_regions);
guarantee(_hrs != NULL, "Couldn't allocate HeapRegionSeq");
- guarantee(_cur_alloc_region == NULL, "from constructor");
// 6843694 - ensure that the maximum region index can fit
// in the remembered set structures.
@@ -2195,6 +1955,22 @@
// Do later initialization work for concurrent refinement.
_cg1r->init();
+ // Here we allocate the dummy full region that is required by the
+ // G1AllocRegion class. If we don't pass an address in the reserved
+ // space here, lots of asserts fire.
+ MemRegion mr(_g1_reserved.start(), HeapRegion::GrainWords);
+ HeapRegion* dummy_region = new HeapRegion(_bot_shared, mr, true);
+ // We'll re-use the same region whether the alloc region will
+ // require BOT updates or not and, if it doesn't, then a non-young
+ // region will complain that it cannot support allocations without
+ // BOT updates. So we'll tag the dummy region as young to avoid that.
+ dummy_region->set_young();
+ // Make sure it's full.
+ dummy_region->set_top(dummy_region->end());
+ G1AllocRegion::setup(this, dummy_region);
+
+ init_mutator_alloc_region();
+
return JNI_OK;
}
@@ -2261,7 +2037,7 @@
"Should be owned on this thread's behalf.");
size_t result = _summary_bytes_used;
// Read only once in case it is set to NULL concurrently
- HeapRegion* hr = _cur_alloc_region;
+ HeapRegion* hr = _mutator_alloc_region.get();
if (hr != NULL)
result += hr->used();
return result;
@@ -2324,13 +2100,11 @@
// to free(), resulting in a SIGSEGV. Note that this doesn't appear
// to be a problem in the optimized build, since the two loads of the
// current allocation region field are optimized away.
- HeapRegion* car = _cur_alloc_region;
-
- // FIXME: should iterate over all regions?
- if (car == NULL) {
+ HeapRegion* hr = _mutator_alloc_region.get();
+ if (hr == NULL) {
return 0;
}
- return car->free();
+ return hr->free();
}
bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
@@ -2781,16 +2555,12 @@
// since we can't allow tlabs to grow big enough to accomodate
// humongous objects.
- // We need to store the cur alloc region locally, since it might change
- // between when we test for NULL and when we use it later.
- ContiguousSpace* cur_alloc_space = _cur_alloc_region;
+ HeapRegion* hr = _mutator_alloc_region.get();
size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
-
- if (cur_alloc_space == NULL) {
+ if (hr == NULL) {
return max_tlab_size;
} else {
- return MIN2(MAX2(cur_alloc_space->free(), (size_t)MinTLABSize),
- max_tlab_size);
+ return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
}
}
@@ -3364,6 +3134,7 @@
}
verify_region_sets_optional();
+ verify_dirty_young_regions();
{
// This call will decide whether this pause is an initial-mark
@@ -3425,8 +3196,8 @@
if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
HandleMark hm; // Discard invalid handles created during verification
+ gclog_or_tty->print(" VerifyBeforeGC:");
prepare_for_verify();
- gclog_or_tty->print(" VerifyBeforeGC:");
Universe::verify(false);
}
@@ -3442,7 +3213,7 @@
// Forget the current alloc region (we might even choose it to be part
// of the collection set!).
- abandon_cur_alloc_region();
+ release_mutator_alloc_region();
// The elapsed time induced by the start time below deliberately elides
// the possible verification above.
@@ -3573,6 +3344,8 @@
g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
#endif // YOUNG_LIST_VERBOSE
+ init_mutator_alloc_region();
+
double end_time_sec = os::elapsedTime();
double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS;
g1_policy()->record_pause_time_ms(pause_time_ms);
@@ -3655,6 +3428,15 @@
return gclab_word_size;
}
+void G1CollectedHeap::init_mutator_alloc_region() {
+ assert(_mutator_alloc_region.get() == NULL, "pre-condition");
+ _mutator_alloc_region.init();
+}
+
+void G1CollectedHeap::release_mutator_alloc_region() {
+ _mutator_alloc_region.release();
+ assert(_mutator_alloc_region.get() == NULL, "post-condition");
+}
void G1CollectedHeap::set_gc_alloc_region(int purpose, HeapRegion* r) {
assert(purpose >= 0 && purpose < GCAllocPurposeCount, "invalid purpose");
@@ -5140,10 +4922,8 @@
CardTableModRefBS* _ct_bs;
public:
G1VerifyCardTableCleanup(CardTableModRefBS* ct_bs)
- : _ct_bs(ct_bs)
- { }
- virtual bool doHeapRegion(HeapRegion* r)
- {
+ : _ct_bs(ct_bs) { }
+ virtual bool doHeapRegion(HeapRegion* r) {
MemRegion mr(r->bottom(), r->end());
if (r->is_survivor()) {
_ct_bs->verify_dirty_region(mr);
@@ -5153,6 +4933,29 @@
return false;
}
};
+
+void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
+ CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
+ for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
+ // We cannot guarantee that [bottom(),end()] is dirty. Threads
+ // dirty allocated blocks as they allocate them. The thread that
+ // retires each region and replaces it with a new one will do a
+ // maximal allocation to fill in [pre_dummy_top(),end()] but will
+ // not dirty that area (one less thing to have to do while holding
+ // a lock). So we can only verify that [bottom(),pre_dummy_top()]
+ // is dirty. Also note that verify_dirty_region() requires
+ // mr.start() and mr.end() to be card aligned and pre_dummy_top()
+ // is not guaranteed to be.
+ MemRegion mr(hr->bottom(),
+ ct_bs->align_to_card_boundary(hr->pre_dummy_top()));
+ ct_bs->verify_dirty_region(mr);
+ }
+}
+
+void G1CollectedHeap::verify_dirty_young_regions() {
+ verify_dirty_young_list(_young_list->first_region());
+ verify_dirty_young_list(_young_list->first_survivor_region());
+}
#endif
void G1CollectedHeap::cleanUpCardTable() {
@@ -5500,6 +5303,44 @@
}
}
+HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
+ bool force) {
+ assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
+ assert(!force || g1_policy()->can_expand_young_list(),
+ "if force is true we should be able to expand the young list");
+ if (force || !g1_policy()->is_young_list_full()) {
+ HeapRegion* new_alloc_region = new_region(word_size,
+ false /* do_expand */);
+ if (new_alloc_region != NULL) {
+ g1_policy()->update_region_num(true /* next_is_young */);
+ set_region_short_lived_locked(new_alloc_region);
+ return new_alloc_region;
+ }
+ }
+ return NULL;
+}
+
+void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
+ size_t allocated_bytes) {
+ assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
+ assert(alloc_region->is_young(), "all mutator alloc regions should be young");
+
+ g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
+ _summary_bytes_used += allocated_bytes;
+}
+
+HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
+ bool force) {
+ return _g1h->new_mutator_alloc_region(word_size, force);
+}
+
+void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
+ size_t allocated_bytes) {
+ _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
+}
+
+// Heap region set verification
+
class VerifyRegionListsClosure : public HeapRegionClosure {
private:
HumongousRegionSet* _humongous_set;
--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp Tue Mar 29 22:36:16 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.hpp Wed Mar 30 10:26:59 2011 -0400
@@ -26,6 +26,7 @@
#define SHARE_VM_GC_IMPLEMENTATION_G1_G1COLLECTEDHEAP_HPP
#include "gc_implementation/g1/concurrentMark.hpp"
+#include "gc_implementation/g1/g1AllocRegion.hpp"
#include "gc_implementation/g1/g1RemSet.hpp"
#include "gc_implementation/g1/heapRegionSets.hpp"
#include "gc_implementation/parNew/parGCAllocBuffer.hpp"
@@ -128,6 +129,15 @@
void print();
};
+class MutatorAllocRegion : public G1AllocRegion {
+protected:
+ virtual HeapRegion* allocate_new_region(size_t word_size, bool force);
+ virtual void retire_region(HeapRegion* alloc_region, size_t allocated_bytes);
+public:
+ MutatorAllocRegion()
+ : G1AllocRegion("Mutator Alloc Region", false /* bot_updates */) { }
+};
+
class RefineCardTableEntryClosure;
class G1CollectedHeap : public SharedHeap {
friend class VM_G1CollectForAllocation;
@@ -135,6 +145,7 @@
friend class VM_G1CollectFull;
friend class VM_G1IncCollectionPause;
friend class VMStructs;
+ friend class MutatorAllocRegion;
// Closures used in implementation.
friend class G1ParCopyHelper;
@@ -197,12 +208,15 @@
// The sequence of all heap regions in the heap.
HeapRegionSeq* _hrs;
- // The region from which normal-sized objects are currently being
- // allocated. May be NULL.
- HeapRegion* _cur_alloc_region;
+ // Alloc region used to satisfy mutator allocation requests.
+ MutatorAllocRegion _mutator_alloc_region;
- // Postcondition: cur_alloc_region == NULL.
- void abandon_cur_alloc_region();
+ // It resets the mutator alloc region before new allocations can take place.
+ void init_mutator_alloc_region();
+
+ // It releases the mutator alloc region.
+ void release_mutator_alloc_region();
+
void abandon_gc_alloc_regions();
// The to-space memory regions into which objects are being copied during
@@ -360,27 +374,21 @@
G1CollectorPolicy* _g1_policy;
// This is the second level of trying to allocate a new region. If
- // new_region_work didn't find a region in the free_list, this call
- // will check whether there's anything available in the
- // secondary_free_list and/or wait for more regions to appear in that
- // list, if _free_regions_coming is set.
+ // new_region() didn't find a region on the free_list, this call will
+ // check whether there's anything available on the
+ // secondary_free_list and/or wait for more regions to appear on
+ // that list, if _free_regions_coming is set.
HeapRegion* new_region_try_secondary_free_list();
// Try to allocate a single non-humongous HeapRegion sufficient for
// an allocation of the given word_size. If do_expand is true,
// attempt to expand the heap if necessary to satisfy the allocation
// request.
- HeapRegion* new_region_work(size_t word_size, bool do_expand);
+ HeapRegion* new_region(size_t word_size, bool do_expand);
- // Try to allocate a new region to be used for allocation by a
- // mutator thread. Attempt to expand the heap if no region is
+ // Try to allocate a new region to be used for allocation by
+ // a GC thread. It will try to expand the heap if no region is
// available.
- HeapRegion* new_alloc_region(size_t word_size) {
- return new_region_work(word_size, false /* do_expand */);
- }
-
- // Try to allocate a new region to be used for allocation by a GC
- // thread. Attempt to expand the heap if no region is available.
HeapRegion* new_gc_alloc_region(int purpose, size_t word_size);
// Attempt to satisfy a humongous allocation request of the given
@@ -415,10 +423,6 @@
// * All non-TLAB allocation requests should go to mem_allocate()
// and mem_allocate() should never be called with is_tlab == true.
//
- // * If the GC locker is active we currently stall until we can
- // allocate a new young region. This will be changed in the
- // near future (see CR 6994056).
- //
// * If either call cannot satisfy the allocation request using the
// current allocating region, they will try to get a new one. If
// this fails, they will attempt to do an evacuation pause and
@@ -441,122 +445,38 @@
bool is_tlab, /* expected to be false */
bool* gc_overhead_limit_was_exceeded);
- // The following methods, allocate_from_cur_allocation_region(),
- // attempt_allocation(), attempt_allocation_locked(),
- // replace_cur_alloc_region_and_allocate(),
- // attempt_allocation_slow(), and attempt_allocation_humongous()
- // have very awkward pre- and post-conditions with respect to
- // locking:
- //
- // If they are called outside a safepoint they assume the caller
- // holds the Heap_lock when it calls them. However, on exit they
- // will release the Heap_lock if they return a non-NULL result, but
- // keep holding the Heap_lock if they return a NULL result. The
- // reason for this is that we need to dirty the cards that span
- // allocated blocks on young regions to avoid having to take the
- // slow path of the write barrier (for performance reasons we don't
- // update RSets for references whose source is a young region, so we
- // don't need to look at dirty cards on young regions). But, doing
- // this card dirtying while holding the Heap_lock can be a
- // scalability bottleneck, especially given that some allocation
- // requests might be of non-trivial size (and the larger the region
- // size is, the fewer allocations requests will be considered
- // humongous, as the humongous size limit is a fraction of the
- // region size). So, when one of these calls succeeds in allocating
- // a block it does the card dirtying after it releases the Heap_lock
- // which is why it will return without holding it.
- //
- // The above assymetry is the reason why locking / unlocking is done
- // explicitly (i.e., with Heap_lock->lock() and
- // Heap_lock->unlocked()) instead of using MutexLocker and
- // MutexUnlocker objects. The latter would ensure that the lock is
- // unlocked / re-locked at every possible exit out of the basic
- // block. However, we only want that action to happen in selected
- // places.
- //
- // Further, if the above methods are called during a safepoint, then
- // naturally there's no assumption about the Heap_lock being held or
- // there's no attempt to unlock it. The parameter at_safepoint
- // indicates whether the call is made during a safepoint or not (as
- // an optimization, to avoid reading the global flag with
- // SafepointSynchronize::is_at_safepoint()).
- //
- // The methods share these parameters:
- //
- // * word_size : the size of the allocation request in words
- // * at_safepoint : whether the call is done at a safepoint; this
- // also determines whether a GC is permitted
- // (at_safepoint == false) or not (at_safepoint == true)
- // * do_dirtying : whether the method should dirty the allocated
- // block before returning
- //
- // They all return either the address of the block, if they
- // successfully manage to allocate it, or NULL.
+ // The following three methods take a gc_count_before_ret
+ // parameter which is used to return the GC count if the method
+ // returns NULL. Given that we are required to read the GC count
+ // while holding the Heap_lock, and these paths will take the
+ // Heap_lock at some point, it's easier to get them to read the GC
+ // count while holding the Heap_lock before they return NULL instead
+ // of the caller (namely: mem_allocate()) having to also take the
+ // Heap_lock just to read the GC count.
+
+ // First-level mutator allocation attempt: try to allocate out of
+ // the mutator alloc region without taking the Heap_lock. This
+ // should only be used for non-humongous allocations.
+ inline HeapWord* attempt_allocation(size_t word_size,
+ unsigned int* gc_count_before_ret);
- // It tries to satisfy an allocation request out of the current
- // alloc region, which is passed as a parameter. It assumes that the
- // caller has checked that the current alloc region is not NULL.
- // Given that the caller has to check the current alloc region for
- // at least NULL, it might as well pass it as the first parameter so
- // that the method doesn't have to read it from the
- // _cur_alloc_region field again. It is called from both
- // attempt_allocation() and attempt_allocation_locked() and the
- // with_heap_lock parameter indicates whether the caller was holding
- // the heap lock when it called it or not.
- inline HeapWord* allocate_from_cur_alloc_region(HeapRegion* cur_alloc_region,
- size_t word_size,
- bool with_heap_lock);
-
- // First-level of allocation slow path: it attempts to allocate out
- // of the current alloc region in a lock-free manner using a CAS. If
- // that fails it takes the Heap_lock and calls
- // attempt_allocation_locked() for the second-level slow path.
- inline HeapWord* attempt_allocation(size_t word_size);
-
- // Second-level of allocation slow path: while holding the Heap_lock
- // it tries to allocate out of the current alloc region and, if that
- // fails, tries to allocate out of a new current alloc region.
- inline HeapWord* attempt_allocation_locked(size_t word_size);
+ // Second-level mutator allocation attempt: take the Heap_lock and
+ // retry the allocation attempt, potentially scheduling a GC
+ // pause. This should only be used for non-humongous allocations.
+ HeapWord* attempt_allocation_slow(size_t word_size,
+ unsigned int* gc_count_before_ret);
- // It assumes that the current alloc region has been retired and
- // tries to allocate a new one. If it's successful, it performs the
- // allocation out of the new current alloc region and updates
- // _cur_alloc_region. Normally, it would try to allocate a new
- // region if the young gen is not full, unless can_expand is true in
- // which case it would always try to allocate a new region.
- HeapWord* replace_cur_alloc_region_and_allocate(size_t word_size,
- bool at_safepoint,
- bool do_dirtying,
- bool can_expand);
-
- // Third-level of allocation slow path: when we are unable to
- // allocate a new current alloc region to satisfy an allocation
- // request (i.e., when attempt_allocation_locked() fails). It will
- // try to do an evacuation pause, which might stall due to the GC
- // locker, and retry the allocation attempt when appropriate.
- HeapWord* attempt_allocation_slow(size_t word_size);
+ // Takes the Heap_lock and attempts a humongous allocation. It can
+ // potentially schedule a GC pause.
+ HeapWord* attempt_allocation_humongous(size_t word_size,
+ unsigned int* gc_count_before_ret);
- // The method that tries to satisfy a humongous allocation
- // request. If it cannot satisfy it it will try to do an evacuation
- // pause to perhaps reclaim enough space to be able to satisfy the
- // allocation request afterwards.
- HeapWord* attempt_allocation_humongous(size_t word_size,
- bool at_safepoint);
-
- // It does the common work when we are retiring the current alloc region.
- inline void retire_cur_alloc_region_common(HeapRegion* cur_alloc_region);
-
- // It retires the current alloc region, which is passed as a
- // parameter (since, typically, the caller is already holding on to
- // it). It sets _cur_alloc_region to NULL.
- void retire_cur_alloc_region(HeapRegion* cur_alloc_region);
-
- // It attempts to do an allocation immediately before or after an
- // evacuation pause and can only be called by the VM thread. It has
- // slightly different assumptions that the ones before (i.e.,
- // assumes that the current alloc region has been retired).
+ // Allocation attempt that should be called during safepoints (e.g.,
+ // at the end of a successful GC). expect_null_mutator_alloc_region
+ // specifies whether the mutator alloc region is expected to be NULL
+ // or not.
HeapWord* attempt_allocation_at_safepoint(size_t word_size,
- bool expect_null_cur_alloc_region);
+ bool expect_null_mutator_alloc_region);
// It dirties the cards that cover the block so that so that the post
// write barrier never queues anything when updating objects on this
@@ -583,6 +503,12 @@
// GC pause.
void retire_alloc_region(HeapRegion* alloc_region, bool par);
+ // These two methods are the "callbacks" from the G1AllocRegion class.
+
+ HeapRegion* new_mutator_alloc_region(size_t word_size, bool force);
+ void retire_mutator_alloc_region(HeapRegion* alloc_region,
+ size_t allocated_bytes);
+
// - if explicit_gc is true, the GC is for a System.gc() or a heap
// inspection request and should collect the entire heap
// - if clear_all_soft_refs is true, all soft references should be
@@ -1027,6 +953,9 @@
// The number of regions available for "regular" expansion.
size_t expansion_regions() { return _expansion_regions; }
+ void verify_dirty_young_list(HeapRegion* head) PRODUCT_RETURN;
+ void verify_dirty_young_regions() PRODUCT_RETURN;
+
// verify_region_sets() performs verification over the region
// lists. It will be compiled in the product code to be used when
// necessary (i.e., during heap verification).
--- a/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.inline.hpp Tue Mar 29 22:36:16 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.inline.hpp Wed Mar 30 10:26:59 2011 -0400
@@ -27,6 +27,7 @@
#include "gc_implementation/g1/concurrentMark.hpp"
#include "gc_implementation/g1/g1CollectedHeap.hpp"
+#include "gc_implementation/g1/g1AllocRegion.inline.hpp"
#include "gc_implementation/g1/g1CollectorPolicy.hpp"
#include "gc_implementation/g1/heapRegionSeq.inline.hpp"
#include "utilities/taskqueue.hpp"
@@ -59,131 +60,23 @@
return r != NULL && r->in_collection_set();
}
-// See the comment in the .hpp file about the locking protocol and
-// assumptions of this method (and other related ones).
inline HeapWord*
-G1CollectedHeap::allocate_from_cur_alloc_region(HeapRegion* cur_alloc_region,
- size_t word_size,
- bool with_heap_lock) {
- assert_not_at_safepoint();
- assert(with_heap_lock == Heap_lock->owned_by_self(),
- "with_heap_lock and Heap_lock->owned_by_self() should be a tautology");
- assert(cur_alloc_region != NULL, "pre-condition of the method");
- assert(cur_alloc_region->is_young(),
- "we only support young current alloc regions");
- assert(!isHumongous(word_size), "allocate_from_cur_alloc_region() "
- "should not be used for humongous allocations");
- assert(!cur_alloc_region->isHumongous(), "Catch a regression of this bug.");
-
- assert(!cur_alloc_region->is_empty(),
- err_msg("region ["PTR_FORMAT","PTR_FORMAT"] should not be empty",
- cur_alloc_region->bottom(), cur_alloc_region->end()));
- HeapWord* result = cur_alloc_region->par_allocate_no_bot_updates(word_size);
- if (result != NULL) {
- assert(is_in(result), "result should be in the heap");
-
- if (with_heap_lock) {
- Heap_lock->unlock();
- }
- assert_heap_not_locked();
- // Do the dirtying after we release the Heap_lock.
- dirty_young_block(result, word_size);
- return result;
- }
-
- if (with_heap_lock) {
- assert_heap_locked();
- } else {
- assert_heap_not_locked();
- }
- return NULL;
-}
-
-// See the comment in the .hpp file about the locking protocol and
-// assumptions of this method (and other related ones).
-inline HeapWord*
-G1CollectedHeap::attempt_allocation(size_t word_size) {
+G1CollectedHeap::attempt_allocation(size_t word_size,
+ unsigned int* gc_count_before_ret) {
assert_heap_not_locked_and_not_at_safepoint();
- assert(!isHumongous(word_size), "attempt_allocation() should not be called "
- "for humongous allocation requests");
-
- HeapRegion* cur_alloc_region = _cur_alloc_region;
- if (cur_alloc_region != NULL) {
- HeapWord* result = allocate_from_cur_alloc_region(cur_alloc_region,
- word_size,
- false /* with_heap_lock */);
- assert_heap_not_locked();
- if (result != NULL) {
- return result;
- }
- }
+ assert(!isHumongous(word_size), "attempt_allocation() should not "
+ "be called for humongous allocation requests");
- // Our attempt to allocate lock-free failed as the current
- // allocation region is either NULL or full. So, we'll now take the
- // Heap_lock and retry.
- Heap_lock->lock();
-
- HeapWord* result = attempt_allocation_locked(word_size);
- if (result != NULL) {
- assert_heap_not_locked();
- return result;
+ HeapWord* result = _mutator_alloc_region.attempt_allocation(word_size,
+ false /* bot_updates */);
+ if (result == NULL) {
+ result = attempt_allocation_slow(word_size, gc_count_before_ret);
}
-
- assert_heap_locked();
- return NULL;
-}
-
-inline void
-G1CollectedHeap::retire_cur_alloc_region_common(HeapRegion* cur_alloc_region) {
- assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
- assert(cur_alloc_region != NULL && cur_alloc_region == _cur_alloc_region,
- "pre-condition of the call");
- assert(cur_alloc_region->is_young(),
- "we only support young current alloc regions");
-
- // The region is guaranteed to be young
- g1_policy()->add_region_to_incremental_cset_lhs(cur_alloc_region);
- _summary_bytes_used += cur_alloc_region->used();
- _cur_alloc_region = NULL;
-}
-
-inline HeapWord*
-G1CollectedHeap::attempt_allocation_locked(size_t word_size) {
- assert_heap_locked_and_not_at_safepoint();
- assert(!isHumongous(word_size), "attempt_allocation_locked() "
- "should not be called for humongous allocation requests");
-
- // First, reread the current alloc region and retry the allocation
- // in case somebody replaced it while we were waiting to get the
- // Heap_lock.
- HeapRegion* cur_alloc_region = _cur_alloc_region;
- if (cur_alloc_region != NULL) {
- HeapWord* result = allocate_from_cur_alloc_region(
- cur_alloc_region, word_size,
- true /* with_heap_lock */);
- if (result != NULL) {
- assert_heap_not_locked();
- return result;
- }
-
- // We failed to allocate out of the current alloc region, so let's
- // retire it before getting a new one.
- retire_cur_alloc_region(cur_alloc_region);
+ assert_heap_not_locked();
+ if (result != NULL) {
+ dirty_young_block(result, word_size);
}
-
- assert_heap_locked();
- // Try to get a new region and allocate out of it
- HeapWord* result = replace_cur_alloc_region_and_allocate(word_size,
- false, /* at_safepoint */
- true, /* do_dirtying */
- false /* can_expand */);
- if (result != NULL) {
- assert_heap_not_locked();
- return result;
- }
-
- assert_heap_locked();
- return NULL;
+ return result;
}
// It dirties the cards that cover the block so that so that the post
--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegion.cpp Tue Mar 29 22:36:16 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegion.cpp Wed Mar 30 10:26:59 2011 -0400
@@ -360,6 +360,7 @@
set_young_index_in_cset(-1);
uninstall_surv_rate_group();
set_young_type(NotYoung);
+ reset_pre_dummy_top();
if (!par) {
// If this is parallel, this will be done later.
@@ -923,11 +924,11 @@
ContiguousSpace::set_saved_mark();
OrderAccess::storestore();
_gc_time_stamp = curr_gc_time_stamp;
- // The following fence is to force a flush of the writes above, but
- // is strictly not needed because when an allocating worker thread
- // calls set_saved_mark() it does so under the ParGCRareEvent_lock;
- // when the lock is released, the write will be flushed.
- // OrderAccess::fence();
+ // No need to do another barrier to flush the writes above. If
+ // this is called in parallel with other threads trying to
+ // allocate into the region, the caller should call this while
+ // holding a lock and when the lock is released the writes will be
+ // flushed.
}
}
--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegion.hpp Tue Mar 29 22:36:16 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegion.hpp Wed Mar 30 10:26:59 2011 -0400
@@ -149,6 +149,13 @@
G1BlockOffsetArrayContigSpace _offsets;
Mutex _par_alloc_lock;
volatile unsigned _gc_time_stamp;
+ // When we need to retire an allocation region, while other threads
+ // are also concurrently trying to allocate into it, we typically
+ // allocate a dummy object at the end of the region to ensure that
+ // no more allocations can take place in it. However, sometimes we
+ // want to know where the end of the last "real" object we allocated
+ // into the region was and this is what this keeps track.
+ HeapWord* _pre_dummy_top;
public:
// Constructor. If "is_zeroed" is true, the MemRegion "mr" may be
@@ -163,6 +170,17 @@
virtual void set_saved_mark();
void reset_gc_time_stamp() { _gc_time_stamp = 0; }
+ // See the comment above in the declaration of _pre_dummy_top for an
+ // explanation of what it is.
+ void set_pre_dummy_top(HeapWord* pre_dummy_top) {
+ assert(is_in(pre_dummy_top) && pre_dummy_top <= top(), "pre-condition");
+ _pre_dummy_top = pre_dummy_top;
+ }
+ HeapWord* pre_dummy_top() {
+ return (_pre_dummy_top == NULL) ? top() : _pre_dummy_top;
+ }
+ void reset_pre_dummy_top() { _pre_dummy_top = NULL; }
+
virtual void initialize(MemRegion mr, bool clear_space, bool mangle_space);
virtual void clear(bool mangle_space);
--- a/hotspot/src/share/vm/gc_implementation/g1/heapRegion.inline.hpp Tue Mar 29 22:36:16 2011 -0400
+++ b/hotspot/src/share/vm/gc_implementation/g1/heapRegion.inline.hpp Wed Mar 30 10:26:59 2011 -0400
@@ -38,15 +38,8 @@
// this is used for larger LAB allocations only.
inline HeapWord* G1OffsetTableContigSpace::par_allocate(size_t size) {
MutexLocker x(&_par_alloc_lock);
- // This ought to be just "allocate", because of the lock above, but that
- // ContiguousSpace::allocate asserts that either the allocating thread
- // holds the heap lock or it is the VM thread and we're at a safepoint.
- // The best I (dld) could figure was to put a field in ContiguousSpace
- // meaning "locking at safepoint taken care of", and set/reset that
- // here. But this will do for now, especially in light of the comment
- // above. Perhaps in the future some lock-free manner of keeping the
- // coordination.
- HeapWord* res = ContiguousSpace::par_allocate(size);
+ // Given that we take the lock no need to use par_allocate() here.
+ HeapWord* res = ContiguousSpace::allocate(size);
if (res != NULL) {
_offsets.alloc_block(res, size);
}
--- a/hotspot/src/share/vm/memory/cardTableModRefBS.hpp Tue Mar 29 22:36:16 2011 -0400
+++ b/hotspot/src/share/vm/memory/cardTableModRefBS.hpp Wed Mar 30 10:26:59 2011 -0400
@@ -382,6 +382,11 @@
return (addr_for(pcard) == p);
}
+ HeapWord* align_to_card_boundary(HeapWord* p) {
+ jbyte* pcard = byte_for(p + card_size_in_words - 1);
+ return addr_for(pcard);
+ }
+
// The kinds of precision a CardTableModRefBS may offer.
enum PrecisionStyle {
Precise,
--- a/hotspot/src/share/vm/memory/space.cpp Tue Mar 29 22:36:16 2011 -0400
+++ b/hotspot/src/share/vm/memory/space.cpp Wed Mar 30 10:26:59 2011 -0400
@@ -818,9 +818,14 @@
// This version requires locking.
inline HeapWord* ContiguousSpace::allocate_impl(size_t size,
HeapWord* const end_value) {
+ // In G1 there are places where a GC worker can allocates into a
+ // region using this serial allocation code without being prone to a
+ // race with other GC workers (we ensure that no other GC worker can
+ // access the same region at the same time). So the assert below is
+ // too strong in the case of G1.
assert(Heap_lock->owned_by_self() ||
(SafepointSynchronize::is_at_safepoint() &&
- Thread::current()->is_VM_thread()),
+ (Thread::current()->is_VM_thread() || UseG1GC)),
"not locked");
HeapWord* obj = top();
if (pointer_delta(end_value, obj) >= size) {