--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/hotspot/src/share/vm/runtime/sweeper.cpp Sat Dec 01 00:00:00 2007 +0000
@@ -0,0 +1,161 @@
+/*
+ * Copyright 1997-2005 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.com if you need additional information or
+ * have any questions.
+ *
+ */
+
+# include "incls/_precompiled.incl"
+# include "incls/_sweeper.cpp.incl"
+
+long NMethodSweeper::_traversals = 0; // No. of stack traversals performed
+CodeBlob* NMethodSweeper::_current = NULL; // Current nmethod
+int NMethodSweeper::_seen = 0 ; // No. of blobs we have currently processed in current pass of CodeCache
+int NMethodSweeper::_invocations = 0; // No. of invocations left until we are completed with this pass
+
+jint NMethodSweeper::_locked_seen = 0;
+jint NMethodSweeper::_not_entrant_seen_on_stack = 0;
+bool NMethodSweeper::_rescan = false;
+
+void NMethodSweeper::sweep() {
+ assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
+ if (!MethodFlushing) return;
+
+ // No need to synchronize access, since this is always executed at a
+ // safepoint. If we aren't in the middle of scan and a rescan
+ // hasn't been requested then just return.
+ if (_current == NULL && !_rescan) return;
+
+ // Make sure CompiledIC_lock in unlocked, since we might update some
+ // inline caches. If it is, we just bail-out and try later.
+ if (CompiledIC_lock->is_locked() || Patching_lock->is_locked()) return;
+
+ // Check for restart
+ assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
+ if (_current == NULL) {
+ _seen = 0;
+ _invocations = NmethodSweepFraction;
+ _current = CodeCache::first();
+ _traversals += 1;
+ if (PrintMethodFlushing) {
+ tty->print_cr("### Sweep: stack traversal %d", _traversals);
+ }
+ Threads::nmethods_do();
+
+ // reset the flags since we started a scan from the beginning.
+ _rescan = false;
+ _locked_seen = 0;
+ _not_entrant_seen_on_stack = 0;
+ }
+
+ if (PrintMethodFlushing && Verbose) {
+ tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_blobs(), _invocations);
+ }
+
+ // We want to visit all nmethods after NmethodSweepFraction invocations.
+ // If invocation is 1 we do the rest
+ int todo = CodeCache::nof_blobs();
+ if (_invocations != 1) {
+ todo = (CodeCache::nof_blobs() - _seen) / _invocations;
+ _invocations--;
+ }
+
+ for(int i = 0; i < todo && _current != NULL; i++) {
+ CodeBlob* next = CodeCache::next(_current); // Read next before we potentially delete current
+ if (_current->is_nmethod()) {
+ process_nmethod((nmethod *)_current);
+ }
+ _seen++;
+ _current = next;
+ }
+ // Because we could stop on a codeBlob other than an nmethod we skip forward
+ // to the next nmethod (if any). codeBlobs other than nmethods can be freed
+ // async to us and make _current invalid while we sleep.
+ while (_current != NULL && !_current->is_nmethod()) {
+ _current = CodeCache::next(_current);
+ }
+
+ if (_current == NULL && !_rescan && (_locked_seen || _not_entrant_seen_on_stack)) {
+ // we've completed a scan without making progress but there were
+ // nmethods we were unable to process either because they were
+ // locked or were still on stack. We don't have to aggresively
+ // clean them up so just stop scanning. We could scan once more
+ // but that complicates the control logic and it's unlikely to
+ // matter much.
+ if (PrintMethodFlushing) {
+ tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
+ }
+ }
+}
+
+
+void NMethodSweeper::process_nmethod(nmethod *nm) {
+ // Skip methods that are currently referenced by the VM
+ if (nm->is_locked_by_vm()) {
+ // But still remember to clean-up inline caches for alive nmethods
+ if (nm->is_alive()) {
+ // Clean-up all inline caches that points to zombie/non-reentrant methods
+ nm->cleanup_inline_caches();
+ } else {
+ _locked_seen++;
+ }
+ return;
+ }
+
+ if (nm->is_zombie()) {
+ // If it is first time, we see nmethod then we mark it. Otherwise,
+ // we reclame it. When we have seen a zombie method twice, we know that
+ // there are no inline caches that referes to it.
+ if (nm->is_marked_for_reclamation()) {
+ assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
+ nm->flush();
+ } else {
+ nm->mark_for_reclamation();
+ _rescan = true;
+ }
+ } else if (nm->is_not_entrant()) {
+ // If there is no current activations of this method on the
+ // stack we can safely convert it to a zombie method
+ if (nm->can_not_entrant_be_converted()) {
+ nm->make_zombie();
+ _rescan = true;
+ } else {
+ // Still alive, clean up its inline caches
+ nm->cleanup_inline_caches();
+ // we coudn't transition this nmethod so don't immediately
+ // request a rescan. If this method stays on the stack for a
+ // long time we don't want to keep rescanning at every safepoint.
+ _not_entrant_seen_on_stack++;
+ }
+ } else if (nm->is_unloaded()) {
+ // Unloaded code, just make it a zombie
+ if (nm->is_osr_only_method()) {
+ // No inline caches will ever point to osr methods, so we can just remove it
+ nm->flush();
+ } else {
+ nm->make_zombie();
+ _rescan = true;
+ }
+ } else {
+ assert(nm->is_alive(), "should be alive");
+ // Clean-up all inline caches that points to zombie/non-reentrant methods
+ nm->cleanup_inline_caches();
+ }
+}