--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/runtime/sweeper.cpp Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,832 @@
+/*
+ * Copyright (c) 1997, 2017, 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 "code/codeCache.hpp"
+#include "code/compiledIC.hpp"
+#include "code/icBuffer.hpp"
+#include "code/nmethod.hpp"
+#include "compiler/compileBroker.hpp"
+#include "logging/log.hpp"
+#include "logging/logStream.hpp"
+#include "memory/resourceArea.hpp"
+#include "oops/method.hpp"
+#include "runtime/atomic.hpp"
+#include "runtime/compilationPolicy.hpp"
+#include "runtime/mutexLocker.hpp"
+#include "runtime/orderAccess.inline.hpp"
+#include "runtime/os.hpp"
+#include "runtime/sweeper.hpp"
+#include "runtime/thread.inline.hpp"
+#include "runtime/vm_operations.hpp"
+#include "trace/tracing.hpp"
+#include "utilities/events.hpp"
+#include "utilities/ticks.inline.hpp"
+#include "utilities/xmlstream.hpp"
+
+#ifdef ASSERT
+
+#define SWEEP(nm) record_sweep(nm, __LINE__)
+// Sweeper logging code
+class SweeperRecord {
+ public:
+ int traversal;
+ int compile_id;
+ long traversal_mark;
+ int state;
+ const char* kind;
+ address vep;
+ address uep;
+ int line;
+
+ void print() {
+ tty->print_cr("traversal = %d compile_id = %d %s uep = " PTR_FORMAT " vep = "
+ PTR_FORMAT " state = %d traversal_mark %ld line = %d",
+ traversal,
+ compile_id,
+ kind == NULL ? "" : kind,
+ p2i(uep),
+ p2i(vep),
+ state,
+ traversal_mark,
+ line);
+ }
+};
+
+static int _sweep_index = 0;
+static SweeperRecord* _records = NULL;
+
+void NMethodSweeper::report_events(int id, address entry) {
+ if (_records != NULL) {
+ for (int i = _sweep_index; i < SweeperLogEntries; i++) {
+ if (_records[i].uep == entry ||
+ _records[i].vep == entry ||
+ _records[i].compile_id == id) {
+ _records[i].print();
+ }
+ }
+ for (int i = 0; i < _sweep_index; i++) {
+ if (_records[i].uep == entry ||
+ _records[i].vep == entry ||
+ _records[i].compile_id == id) {
+ _records[i].print();
+ }
+ }
+ }
+}
+
+void NMethodSweeper::report_events() {
+ if (_records != NULL) {
+ for (int i = _sweep_index; i < SweeperLogEntries; i++) {
+ // skip empty records
+ if (_records[i].vep == NULL) continue;
+ _records[i].print();
+ }
+ for (int i = 0; i < _sweep_index; i++) {
+ // skip empty records
+ if (_records[i].vep == NULL) continue;
+ _records[i].print();
+ }
+ }
+}
+
+void NMethodSweeper::record_sweep(CompiledMethod* nm, int line) {
+ if (_records != NULL) {
+ _records[_sweep_index].traversal = _traversals;
+ _records[_sweep_index].traversal_mark = nm->is_nmethod() ? ((nmethod*)nm)->stack_traversal_mark() : 0;
+ _records[_sweep_index].compile_id = nm->compile_id();
+ _records[_sweep_index].kind = nm->compile_kind();
+ _records[_sweep_index].state = nm->get_state();
+ _records[_sweep_index].vep = nm->verified_entry_point();
+ _records[_sweep_index].uep = nm->entry_point();
+ _records[_sweep_index].line = line;
+ _sweep_index = (_sweep_index + 1) % SweeperLogEntries;
+ }
+}
+
+void NMethodSweeper::init_sweeper_log() {
+ if (LogSweeper && _records == NULL) {
+ // Create the ring buffer for the logging code
+ _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
+ memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
+ }
+}
+#else
+#define SWEEP(nm)
+#endif
+
+CompiledMethodIterator NMethodSweeper::_current; // Current compiled method
+long NMethodSweeper::_traversals = 0; // Stack scan count, also sweep ID.
+long NMethodSweeper::_total_nof_code_cache_sweeps = 0; // Total number of full sweeps of the code cache
+long NMethodSweeper::_time_counter = 0; // Virtual time used to periodically invoke sweeper
+long NMethodSweeper::_last_sweep = 0; // Value of _time_counter when the last sweep happened
+int NMethodSweeper::_seen = 0; // Nof. nmethod we have currently processed in current pass of CodeCache
+
+volatile bool NMethodSweeper::_should_sweep = true; // Indicates if we should invoke the sweeper
+volatile bool NMethodSweeper::_force_sweep = false;// Indicates if we should force a sweep
+volatile int NMethodSweeper::_bytes_changed = 0; // Counts the total nmethod size if the nmethod changed from:
+ // 1) alive -> not_entrant
+ // 2) not_entrant -> zombie
+int NMethodSweeper::_hotness_counter_reset_val = 0;
+
+long NMethodSweeper::_total_nof_methods_reclaimed = 0; // Accumulated nof methods flushed
+long NMethodSweeper::_total_nof_c2_methods_reclaimed = 0; // Accumulated nof methods flushed
+size_t NMethodSweeper::_total_flushed_size = 0; // Total number of bytes flushed from the code cache
+Tickspan NMethodSweeper::_total_time_sweeping; // Accumulated time sweeping
+Tickspan NMethodSweeper::_total_time_this_sweep; // Total time this sweep
+Tickspan NMethodSweeper::_peak_sweep_time; // Peak time for a full sweep
+Tickspan NMethodSweeper::_peak_sweep_fraction_time; // Peak time sweeping one fraction
+
+Monitor* NMethodSweeper::_stat_lock = new Monitor(Mutex::special, "Sweeper::Statistics", true, Monitor::_safepoint_check_sometimes);
+
+class MarkActivationClosure: public CodeBlobClosure {
+public:
+ virtual void do_code_blob(CodeBlob* cb) {
+ assert(cb->is_nmethod(), "CodeBlob should be nmethod");
+ nmethod* nm = (nmethod*)cb;
+ nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
+ // If we see an activation belonging to a non_entrant nmethod, we mark it.
+ if (nm->is_not_entrant()) {
+ nm->mark_as_seen_on_stack();
+ }
+ }
+};
+static MarkActivationClosure mark_activation_closure;
+
+class SetHotnessClosure: public CodeBlobClosure {
+public:
+ virtual void do_code_blob(CodeBlob* cb) {
+ assert(cb->is_nmethod(), "CodeBlob should be nmethod");
+ nmethod* nm = (nmethod*)cb;
+ nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
+ }
+};
+static SetHotnessClosure set_hotness_closure;
+
+
+int NMethodSweeper::hotness_counter_reset_val() {
+ if (_hotness_counter_reset_val == 0) {
+ _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2;
+ }
+ return _hotness_counter_reset_val;
+}
+bool NMethodSweeper::wait_for_stack_scanning() {
+ return _current.end();
+}
+
+/**
+ * Scans the stacks of all Java threads and marks activations of not-entrant methods.
+ * No need to synchronize access, since 'mark_active_nmethods' is always executed at a
+ * safepoint.
+ */
+void NMethodSweeper::mark_active_nmethods() {
+ CodeBlobClosure* cl = prepare_mark_active_nmethods();
+ if (cl != NULL) {
+ Threads::nmethods_do(cl);
+ }
+}
+
+CodeBlobClosure* NMethodSweeper::prepare_mark_active_nmethods() {
+ assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
+ // If we do not want to reclaim not-entrant or zombie methods there is no need
+ // to scan stacks
+ if (!MethodFlushing) {
+ return NULL;
+ }
+
+ // Increase time so that we can estimate when to invoke the sweeper again.
+ _time_counter++;
+
+ // Check for restart
+ if (_current.method() != NULL) {
+ if (_current.method()->is_nmethod()) {
+ assert(CodeCache::find_blob_unsafe(_current.method()) == _current.method(), "Sweeper nmethod cached state invalid");
+ } else if (_current.method()->is_aot()) {
+ assert(CodeCache::find_blob_unsafe(_current.method()->code_begin()) == _current.method(), "Sweeper AOT method cached state invalid");
+ } else {
+ ShouldNotReachHere();
+ }
+ }
+
+ if (wait_for_stack_scanning()) {
+ _seen = 0;
+ _current = CompiledMethodIterator();
+ // Initialize to first nmethod
+ _current.next();
+ _traversals += 1;
+ _total_time_this_sweep = Tickspan();
+
+ if (PrintMethodFlushing) {
+ tty->print_cr("### Sweep: stack traversal %ld", _traversals);
+ }
+ return &mark_activation_closure;
+
+ } else {
+ // Only set hotness counter
+ return &set_hotness_closure;
+ }
+
+}
+
+/**
+ * This function triggers a VM operation that does stack scanning of active
+ * methods. Stack scanning is mandatory for the sweeper to make progress.
+ */
+void NMethodSweeper::do_stack_scanning() {
+ assert(!CodeCache_lock->owned_by_self(), "just checking");
+ if (wait_for_stack_scanning()) {
+ VM_MarkActiveNMethods op;
+ VMThread::execute(&op);
+ _should_sweep = true;
+ }
+}
+
+void NMethodSweeper::sweeper_loop() {
+ bool timeout;
+ while (true) {
+ {
+ ThreadBlockInVM tbivm(JavaThread::current());
+ MutexLockerEx waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag);
+ const long wait_time = 60*60*24 * 1000;
+ timeout = CodeCache_lock->wait(Mutex::_no_safepoint_check_flag, wait_time);
+ }
+ if (!timeout) {
+ possibly_sweep();
+ }
+ }
+}
+
+/**
+ * Wakes up the sweeper thread to possibly sweep.
+ */
+void NMethodSweeper::notify(int code_blob_type) {
+ // Makes sure that we do not invoke the sweeper too often during startup.
+ double start_threshold = 100.0 / (double)StartAggressiveSweepingAt;
+ double aggressive_sweep_threshold = MIN2(start_threshold, 1.1);
+ if (CodeCache::reverse_free_ratio(code_blob_type) >= aggressive_sweep_threshold) {
+ assert_locked_or_safepoint(CodeCache_lock);
+ CodeCache_lock->notify();
+ }
+}
+
+/**
+ * Wakes up the sweeper thread and forces a sweep. Blocks until it finished.
+ */
+void NMethodSweeper::force_sweep() {
+ ThreadBlockInVM tbivm(JavaThread::current());
+ MutexLockerEx waiter(CodeCache_lock, Mutex::_no_safepoint_check_flag);
+ // Request forced sweep
+ _force_sweep = true;
+ while (_force_sweep) {
+ // Notify sweeper that we want to force a sweep and wait for completion.
+ // In case a sweep currently takes place we timeout and try again because
+ // we want to enforce a full sweep.
+ CodeCache_lock->notify();
+ CodeCache_lock->wait(Mutex::_no_safepoint_check_flag, 1000);
+ }
+}
+
+/**
+ * Handle a safepoint request
+ */
+void NMethodSweeper::handle_safepoint_request() {
+ if (SafepointSynchronize::is_synchronizing()) {
+ if (PrintMethodFlushing && Verbose) {
+ tty->print_cr("### Sweep at %d out of %d, yielding to safepoint", _seen, CodeCache::nmethod_count());
+ }
+ MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
+
+ JavaThread* thread = JavaThread::current();
+ ThreadBlockInVM tbivm(thread);
+ thread->java_suspend_self();
+ }
+}
+
+/**
+ * This function invokes the sweeper if at least one of the three conditions is met:
+ * (1) The code cache is getting full
+ * (2) There are sufficient state changes in/since the last sweep.
+ * (3) We have not been sweeping for 'some time'
+ */
+void NMethodSweeper::possibly_sweep() {
+ assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
+ // If there was no state change while nmethod sweeping, 'should_sweep' will be false.
+ // This is one of the two places where should_sweep can be set to true. The general
+ // idea is as follows: If there is enough free space in the code cache, there is no
+ // need to invoke the sweeper. The following formula (which determines whether to invoke
+ // the sweeper or not) depends on the assumption that for larger ReservedCodeCacheSizes
+ // we need less frequent sweeps than for smaller ReservedCodecCacheSizes. Furthermore,
+ // the formula considers how much space in the code cache is currently used. Here are
+ // some examples that will (hopefully) help in understanding.
+ //
+ // Small ReservedCodeCacheSizes: (e.g., < 16M) We invoke the sweeper every time, since
+ // the result of the division is 0. This
+ // keeps the used code cache size small
+ // (important for embedded Java)
+ // Large ReservedCodeCacheSize : (e.g., 256M + code cache is 10% full). The formula
+ // computes: (256 / 16) - 1 = 15
+ // As a result, we invoke the sweeper after
+ // 15 invocations of 'mark_active_nmethods.
+ // Large ReservedCodeCacheSize: (e.g., 256M + code Cache is 90% full). The formula
+ // computes: (256 / 16) - 10 = 6.
+ if (!_should_sweep) {
+ const int time_since_last_sweep = _time_counter - _last_sweep;
+ // ReservedCodeCacheSize has an 'unsigned' type. We need a 'signed' type for max_wait_time,
+ // since 'time_since_last_sweep' can be larger than 'max_wait_time'. If that happens using
+ // an unsigned type would cause an underflow (wait_until_next_sweep becomes a large positive
+ // value) that disables the intended periodic sweeps.
+ const int max_wait_time = ReservedCodeCacheSize / (16 * M);
+ double wait_until_next_sweep = max_wait_time - time_since_last_sweep -
+ MAX2(CodeCache::reverse_free_ratio(CodeBlobType::MethodProfiled),
+ CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled));
+ assert(wait_until_next_sweep <= (double)max_wait_time, "Calculation of code cache sweeper interval is incorrect");
+
+ if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) {
+ _should_sweep = true;
+ }
+ }
+
+ // Remember if this was a forced sweep
+ bool forced = _force_sweep;
+
+ // Force stack scanning if there is only 10% free space in the code cache.
+ // We force stack scanning only if the non-profiled code heap gets full, since critical
+ // allocations go to the non-profiled heap and we must be make sure that there is
+ // enough space.
+ double free_percent = 1 / CodeCache::reverse_free_ratio(CodeBlobType::MethodNonProfiled) * 100;
+ if (free_percent <= StartAggressiveSweepingAt) {
+ do_stack_scanning();
+ }
+
+ if (_should_sweep || forced) {
+ init_sweeper_log();
+ sweep_code_cache();
+ }
+
+ // We are done with sweeping the code cache once.
+ _total_nof_code_cache_sweeps++;
+ _last_sweep = _time_counter;
+ // Reset flag; temporarily disables sweeper
+ _should_sweep = false;
+ // If there was enough state change, 'possibly_enable_sweeper()'
+ // sets '_should_sweep' to true
+ possibly_enable_sweeper();
+ // Reset _bytes_changed only if there was enough state change. _bytes_changed
+ // can further increase by calls to 'report_state_change'.
+ if (_should_sweep) {
+ _bytes_changed = 0;
+ }
+
+ if (forced) {
+ // Notify requester that forced sweep finished
+ assert(_force_sweep, "Should be a forced sweep");
+ MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
+ _force_sweep = false;
+ CodeCache_lock->notify();
+ }
+}
+
+void NMethodSweeper::sweep_code_cache() {
+ ResourceMark rm;
+ Ticks sweep_start_counter = Ticks::now();
+
+ log_debug(codecache, sweep, start)("CodeCache flushing");
+
+ int flushed_count = 0;
+ int zombified_count = 0;
+ int flushed_c2_count = 0;
+
+ if (PrintMethodFlushing && Verbose) {
+ tty->print_cr("### Sweep at %d out of %d", _seen, CodeCache::nmethod_count());
+ }
+
+ int swept_count = 0;
+ assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
+ assert(!CodeCache_lock->owned_by_self(), "just checking");
+
+ int freed_memory = 0;
+ {
+ MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
+
+ while (!_current.end()) {
+ swept_count++;
+ // Since we will give up the CodeCache_lock, always skip ahead
+ // to the next nmethod. Other blobs can be deleted by other
+ // threads but nmethods are only reclaimed by the sweeper.
+ CompiledMethod* nm = _current.method();
+ _current.next();
+
+ // Now ready to process nmethod and give up CodeCache_lock
+ {
+ MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
+ // Save information before potentially flushing the nmethod
+ // Only flushing nmethods so size only matters for them.
+ int size = nm->is_nmethod() ? ((nmethod*)nm)->total_size() : 0;
+ bool is_c2_method = nm->is_compiled_by_c2();
+ bool is_osr = nm->is_osr_method();
+ int compile_id = nm->compile_id();
+ intptr_t address = p2i(nm);
+ const char* state_before = nm->state();
+ const char* state_after = "";
+
+ MethodStateChange type = process_compiled_method(nm);
+ switch (type) {
+ case Flushed:
+ state_after = "flushed";
+ freed_memory += size;
+ ++flushed_count;
+ if (is_c2_method) {
+ ++flushed_c2_count;
+ }
+ break;
+ case MadeZombie:
+ state_after = "made zombie";
+ ++zombified_count;
+ break;
+ case None:
+ break;
+ default:
+ ShouldNotReachHere();
+ }
+ if (PrintMethodFlushing && Verbose && type != None) {
+ tty->print_cr("### %s nmethod %3d/" PTR_FORMAT " (%s) %s", is_osr ? "osr" : "", compile_id, address, state_before, state_after);
+ }
+ }
+
+ _seen++;
+ handle_safepoint_request();
+ }
+ }
+
+ assert(_current.end(), "must have scanned the whole cache");
+
+ const Ticks sweep_end_counter = Ticks::now();
+ const Tickspan sweep_time = sweep_end_counter - sweep_start_counter;
+ {
+ MutexLockerEx mu(_stat_lock, Mutex::_no_safepoint_check_flag);
+ _total_time_sweeping += sweep_time;
+ _total_time_this_sweep += sweep_time;
+ _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);
+ _total_flushed_size += freed_memory;
+ _total_nof_methods_reclaimed += flushed_count;
+ _total_nof_c2_methods_reclaimed += flushed_c2_count;
+ _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep);
+ }
+ EventSweepCodeCache event(UNTIMED);
+ if (event.should_commit()) {
+ event.set_starttime(sweep_start_counter);
+ event.set_endtime(sweep_end_counter);
+ event.set_sweepId(_traversals);
+ event.set_sweptCount(swept_count);
+ event.set_flushedCount(flushed_count);
+ event.set_zombifiedCount(zombified_count);
+ event.commit();
+ }
+
+#ifdef ASSERT
+ if(PrintMethodFlushing) {
+ tty->print_cr("### sweeper: sweep time(" JLONG_FORMAT "): ", sweep_time.value());
+ }
+#endif
+
+ Log(codecache, sweep) log;
+ if (log.is_debug()) {
+ LogStream ls(log.debug());
+ CodeCache::print_summary(&ls, false);
+ }
+ log_sweep("finished");
+
+ // Sweeper is the only case where memory is released, check here if it
+ // is time to restart the compiler. Only checking if there is a certain
+ // amount of free memory in the code cache might lead to re-enabling
+ // compilation although no memory has been released. For example, there are
+ // cases when compilation was disabled although there is 4MB (or more) free
+ // memory in the code cache. The reason is code cache fragmentation. Therefore,
+ // it only makes sense to re-enable compilation if we have actually freed memory.
+ // Note that typically several kB are released for sweeping 16MB of the code
+ // cache. As a result, 'freed_memory' > 0 to restart the compiler.
+ if (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0)) {
+ CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
+ log.debug("restart compiler");
+ log_sweep("restart_compiler");
+ }
+}
+
+/**
+ * This function updates the sweeper statistics that keep track of nmethods
+ * state changes. If there is 'enough' state change, the sweeper is invoked
+ * as soon as possible. There can be data races on _bytes_changed. The data
+ * races are benign, since it does not matter if we loose a couple of bytes.
+ * In the worst case we call the sweeper a little later. Also, we are guaranteed
+ * to invoke the sweeper if the code cache gets full.
+ */
+void NMethodSweeper::report_state_change(nmethod* nm) {
+ _bytes_changed += nm->total_size();
+ possibly_enable_sweeper();
+}
+
+/**
+ * Function determines if there was 'enough' state change in the code cache to invoke
+ * the sweeper again. Currently, we determine 'enough' as more than 1% state change in
+ * the code cache since the last sweep.
+ */
+void NMethodSweeper::possibly_enable_sweeper() {
+ double percent_changed = ((double)_bytes_changed / (double)ReservedCodeCacheSize) * 100;
+ if (percent_changed > 1.0) {
+ _should_sweep = true;
+ }
+}
+
+class CompiledMethodMarker: public StackObj {
+ private:
+ CodeCacheSweeperThread* _thread;
+ public:
+ CompiledMethodMarker(CompiledMethod* cm) {
+ JavaThread* current = JavaThread::current();
+ assert (current->is_Code_cache_sweeper_thread(), "Must be");
+ _thread = (CodeCacheSweeperThread*)current;
+ if (!cm->is_zombie() && !cm->is_unloaded()) {
+ // Only expose live nmethods for scanning
+ _thread->set_scanned_compiled_method(cm);
+ }
+ }
+ ~CompiledMethodMarker() {
+ _thread->set_scanned_compiled_method(NULL);
+ }
+};
+
+void NMethodSweeper::release_compiled_method(CompiledMethod* nm) {
+ // Make sure the released nmethod is no longer referenced by the sweeper thread
+ CodeCacheSweeperThread* thread = (CodeCacheSweeperThread*)JavaThread::current();
+ thread->set_scanned_compiled_method(NULL);
+
+ // Clean up any CompiledICHolders
+ {
+ ResourceMark rm;
+ MutexLocker ml_patch(CompiledIC_lock);
+ RelocIterator iter(nm);
+ while (iter.next()) {
+ if (iter.type() == relocInfo::virtual_call_type) {
+ CompiledIC::cleanup_call_site(iter.virtual_call_reloc(), nm);
+ }
+ }
+ }
+
+ MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
+ nm->flush();
+}
+
+NMethodSweeper::MethodStateChange NMethodSweeper::process_compiled_method(CompiledMethod* cm) {
+ assert(cm != NULL, "sanity");
+ assert(!CodeCache_lock->owned_by_self(), "just checking");
+
+ MethodStateChange result = None;
+ // Make sure this nmethod doesn't get unloaded during the scan,
+ // since safepoints may happen during acquired below locks.
+ CompiledMethodMarker nmm(cm);
+ SWEEP(cm);
+
+ // Skip methods that are currently referenced by the VM
+ if (cm->is_locked_by_vm()) {
+ // But still remember to clean-up inline caches for alive nmethods
+ if (cm->is_alive()) {
+ // Clean inline caches that point to zombie/non-entrant/unloaded nmethods
+ MutexLocker cl(CompiledIC_lock);
+ cm->cleanup_inline_caches();
+ SWEEP(cm);
+ }
+ return result;
+ }
+
+ if (cm->is_zombie()) {
+ // All inline caches that referred to this nmethod were cleaned in the
+ // previous sweeper cycle. Now flush the nmethod from the code cache.
+ assert(!cm->is_locked_by_vm(), "must not flush locked Compiled Methods");
+ release_compiled_method(cm);
+ assert(result == None, "sanity");
+ result = Flushed;
+ } else if (cm->is_not_entrant()) {
+ // If there are no current activations of this method on the
+ // stack we can safely convert it to a zombie method
+ OrderAccess::loadload(); // _stack_traversal_mark and _state
+ if (cm->can_convert_to_zombie()) {
+ // Clear ICStubs to prevent back patching stubs of zombie or flushed
+ // nmethods during the next safepoint (see ICStub::finalize).
+ {
+ MutexLocker cl(CompiledIC_lock);
+ cm->clear_ic_stubs();
+ }
+ // Code cache state change is tracked in make_zombie()
+ cm->make_zombie();
+ SWEEP(cm);
+ // The nmethod may have been locked by JVMTI after being made zombie (see
+ // JvmtiDeferredEvent::compiled_method_unload_event()). If so, we cannot
+ // flush the osr nmethod directly but have to wait for a later sweeper cycle.
+ if (cm->is_osr_method() && !cm->is_locked_by_vm()) {
+ // No inline caches will ever point to osr methods, so we can just remove it.
+ // Make sure that we unregistered the nmethod with the heap and flushed all
+ // dependencies before removing the nmethod (done in make_zombie()).
+ assert(cm->is_zombie(), "nmethod must be unregistered");
+ release_compiled_method(cm);
+ assert(result == None, "sanity");
+ result = Flushed;
+ } else {
+ assert(result == None, "sanity");
+ result = MadeZombie;
+ assert(cm->is_zombie(), "nmethod must be zombie");
+ }
+ } else {
+ // Still alive, clean up its inline caches
+ MutexLocker cl(CompiledIC_lock);
+ cm->cleanup_inline_caches();
+ SWEEP(cm);
+ }
+ } else if (cm->is_unloaded()) {
+ // Code is unloaded, so there are no activations on the stack.
+ // Convert the nmethod to zombie or flush it directly in the OSR case.
+ {
+ // Clean ICs of unloaded nmethods as well because they may reference other
+ // unloaded nmethods that may be flushed earlier in the sweeper cycle.
+ MutexLocker cl(CompiledIC_lock);
+ cm->cleanup_inline_caches();
+ }
+ if (cm->is_osr_method()) {
+ SWEEP(cm);
+ // No inline caches will ever point to osr methods, so we can just remove it
+ release_compiled_method(cm);
+ assert(result == None, "sanity");
+ result = Flushed;
+ } else {
+ // Code cache state change is tracked in make_zombie()
+ cm->make_zombie();
+ SWEEP(cm);
+ assert(result == None, "sanity");
+ result = MadeZombie;
+ }
+ } else {
+ if (cm->is_nmethod()) {
+ possibly_flush((nmethod*)cm);
+ }
+ // Clean inline caches that point to zombie/non-entrant/unloaded nmethods
+ MutexLocker cl(CompiledIC_lock);
+ cm->cleanup_inline_caches();
+ SWEEP(cm);
+ }
+ return result;
+}
+
+
+void NMethodSweeper::possibly_flush(nmethod* nm) {
+ if (UseCodeCacheFlushing) {
+ if (!nm->is_locked_by_vm() && !nm->is_native_method()) {
+ bool make_not_entrant = false;
+
+ // Do not make native methods not-entrant
+ nm->dec_hotness_counter();
+ // Get the initial value of the hotness counter. This value depends on the
+ // ReservedCodeCacheSize
+ int reset_val = hotness_counter_reset_val();
+ int time_since_reset = reset_val - nm->hotness_counter();
+ int code_blob_type = CodeCache::get_code_blob_type(nm);
+ double threshold = -reset_val + (CodeCache::reverse_free_ratio(code_blob_type) * NmethodSweepActivity);
+ // The less free space in the code cache we have - the bigger reverse_free_ratio() is.
+ // I.e., 'threshold' increases with lower available space in the code cache and a higher
+ // NmethodSweepActivity. If the current hotness counter - which decreases from its initial
+ // value until it is reset by stack walking - is smaller than the computed threshold, the
+ // corresponding nmethod is considered for removal.
+ if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > MinPassesBeforeFlush)) {
+ // A method is marked as not-entrant if the method is
+ // 1) 'old enough': nm->hotness_counter() < threshold
+ // 2) The method was in_use for a minimum amount of time: (time_since_reset > MinPassesBeforeFlush)
+ // The second condition is necessary if we are dealing with very small code cache
+ // sizes (e.g., <10m) and the code cache size is too small to hold all hot methods.
+ // The second condition ensures that methods are not immediately made not-entrant
+ // after compilation.
+ make_not_entrant = true;
+ }
+
+ // The stack-scanning low-cost detection may not see the method was used (which can happen for
+ // flat profiles). Check the age counter for possible data.
+ if (UseCodeAging && make_not_entrant && (nm->is_compiled_by_c2() || nm->is_compiled_by_c1())) {
+ MethodCounters* mc = nm->method()->get_method_counters(Thread::current());
+ if (mc != NULL) {
+ // Snapshot the value as it's changed concurrently
+ int age = mc->nmethod_age();
+ if (MethodCounters::is_nmethod_hot(age)) {
+ // The method has gone through flushing, and it became relatively hot that it deopted
+ // before we could take a look at it. Give it more time to appear in the stack traces,
+ // proportional to the number of deopts.
+ MethodData* md = nm->method()->method_data();
+ if (md != NULL && time_since_reset > (int)(MinPassesBeforeFlush * (md->tenure_traps() + 1))) {
+ // It's been long enough, we still haven't seen it on stack.
+ // Try to flush it, but enable counters the next time.
+ mc->reset_nmethod_age();
+ } else {
+ make_not_entrant = false;
+ }
+ } else if (MethodCounters::is_nmethod_warm(age)) {
+ // Method has counters enabled, and the method was used within
+ // previous MinPassesBeforeFlush sweeps. Reset the counter. Stay in the existing
+ // compiled state.
+ mc->reset_nmethod_age();
+ // delay the next check
+ nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());
+ make_not_entrant = false;
+ } else if (MethodCounters::is_nmethod_age_unset(age)) {
+ // No counters were used before. Set the counters to the detection
+ // limit value. If the method is going to be used again it will be compiled
+ // with counters that we're going to use for analysis the the next time.
+ mc->reset_nmethod_age();
+ } else {
+ // Method was totally idle for 10 sweeps
+ // The counter already has the initial value, flush it and may be recompile
+ // later with counters
+ }
+ }
+ }
+
+ if (make_not_entrant) {
+ nm->make_not_entrant();
+
+ // Code cache state change is tracked in make_not_entrant()
+ if (PrintMethodFlushing && Verbose) {
+ tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f",
+ nm->compile_id(), p2i(nm), nm->hotness_counter(), reset_val, threshold);
+ }
+ }
+ }
+ }
+}
+
+// Print out some state information about the current sweep and the
+// state of the code cache if it's requested.
+void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {
+ if (PrintMethodFlushing) {
+ ResourceMark rm;
+ stringStream s;
+ // Dump code cache state into a buffer before locking the tty,
+ // because log_state() will use locks causing lock conflicts.
+ CodeCache::log_state(&s);
+
+ ttyLocker ttyl;
+ tty->print("### sweeper: %s ", msg);
+ if (format != NULL) {
+ va_list ap;
+ va_start(ap, format);
+ tty->vprint(format, ap);
+ va_end(ap);
+ }
+ tty->print_cr("%s", s.as_string());
+ }
+
+ if (LogCompilation && (xtty != NULL)) {
+ ResourceMark rm;
+ stringStream s;
+ // Dump code cache state into a buffer before locking the tty,
+ // because log_state() will use locks causing lock conflicts.
+ CodeCache::log_state(&s);
+
+ ttyLocker ttyl;
+ xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count());
+ if (format != NULL) {
+ va_list ap;
+ va_start(ap, format);
+ xtty->vprint(format, ap);
+ va_end(ap);
+ }
+ xtty->print("%s", s.as_string());
+ xtty->stamp();
+ xtty->end_elem();
+ }
+}
+
+void NMethodSweeper::print() {
+ ttyLocker ttyl;
+ tty->print_cr("Code cache sweeper statistics:");
+ tty->print_cr(" Total sweep time: %1.0lfms", (double)_total_time_sweeping.value()/1000000);
+ tty->print_cr(" Total number of full sweeps: %ld", _total_nof_code_cache_sweeps);
+ tty->print_cr(" Total number of flushed methods: %ld(%ld C2 methods)", _total_nof_methods_reclaimed,
+ _total_nof_c2_methods_reclaimed);
+ tty->print_cr(" Total size of flushed methods: " SIZE_FORMAT "kB", _total_flushed_size/K);
+}