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/*
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* Copyright 1997-2009 Sun Microsystems, Inc. All Rights Reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
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* CA 95054 USA or visit www.sun.com if you need additional information or
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* have any questions.
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*
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*/
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# include "incls/_precompiled.incl"
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# include "incls/_sweeper.cpp.incl"
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long NMethodSweeper::_traversals = 0; // No. of stack traversals performed
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CodeBlob* NMethodSweeper::_current = NULL; // Current nmethod
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int NMethodSweeper::_seen = 0 ; // No. of blobs we have currently processed in current pass of CodeCache
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int NMethodSweeper::_invocations = 0; // No. of invocations left until we are completed with this pass
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jint NMethodSweeper::_locked_seen = 0;
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jint NMethodSweeper::_not_entrant_seen_on_stack = 0;
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bool NMethodSweeper::_rescan = false;
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bool NMethodSweeper::_was_full = false;
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jint NMethodSweeper::_advise_to_sweep = 0;
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jlong NMethodSweeper::_last_was_full = 0;
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uint NMethodSweeper::_highest_marked = 0;
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long NMethodSweeper::_was_full_traversal = 0;
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1
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3908
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class MarkActivationClosure: public CodeBlobClosure {
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public:
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virtual void do_code_blob(CodeBlob* cb) {
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// If we see an activation belonging to a non_entrant nmethod, we mark it.
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if (cb->is_nmethod() && ((nmethod*)cb)->is_not_entrant()) {
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((nmethod*)cb)->mark_as_seen_on_stack();
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}
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}
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};
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static MarkActivationClosure mark_activation_closure;
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1
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void NMethodSweeper::sweep() {
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assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
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if (!MethodFlushing) return;
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// No need to synchronize access, since this is always executed at a
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// safepoint. If we aren't in the middle of scan and a rescan
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// hasn't been requested then just return.
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if (_current == NULL && !_rescan) return;
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// Make sure CompiledIC_lock in unlocked, since we might update some
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// inline caches. If it is, we just bail-out and try later.
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if (CompiledIC_lock->is_locked() || Patching_lock->is_locked()) return;
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// Check for restart
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assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
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if (_current == NULL) {
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_seen = 0;
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_invocations = NmethodSweepFraction;
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_current = CodeCache::first();
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_traversals += 1;
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if (PrintMethodFlushing) {
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tty->print_cr("### Sweep: stack traversal %d", _traversals);
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}
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Threads::nmethods_do(&mark_activation_closure);
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1
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// reset the flags since we started a scan from the beginning.
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_rescan = false;
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_locked_seen = 0;
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_not_entrant_seen_on_stack = 0;
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}
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if (PrintMethodFlushing && Verbose) {
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tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_blobs(), _invocations);
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}
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// We want to visit all nmethods after NmethodSweepFraction invocations.
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// If invocation is 1 we do the rest
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int todo = CodeCache::nof_blobs();
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if (_invocations != 1) {
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todo = (CodeCache::nof_blobs() - _seen) / _invocations;
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_invocations--;
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}
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for(int i = 0; i < todo && _current != NULL; i++) {
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CodeBlob* next = CodeCache::next(_current); // Read next before we potentially delete current
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if (_current->is_nmethod()) {
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process_nmethod((nmethod *)_current);
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}
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_seen++;
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_current = next;
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}
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// Because we could stop on a codeBlob other than an nmethod we skip forward
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// to the next nmethod (if any). codeBlobs other than nmethods can be freed
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// async to us and make _current invalid while we sleep.
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while (_current != NULL && !_current->is_nmethod()) {
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_current = CodeCache::next(_current);
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}
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if (_current == NULL && !_rescan && (_locked_seen || _not_entrant_seen_on_stack)) {
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// we've completed a scan without making progress but there were
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// nmethods we were unable to process either because they were
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// locked or were still on stack. We don't have to aggresively
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// clean them up so just stop scanning. We could scan once more
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// but that complicates the control logic and it's unlikely to
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// matter much.
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if (PrintMethodFlushing) {
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tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
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}
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}
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if (UseCodeCacheFlushing) {
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if (!CodeCache::needs_flushing()) {
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// In a safepoint, no race with setters
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_advise_to_sweep = 0;
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}
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if (was_full()) {
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// There was some progress so attempt to restart the compiler
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jlong now = os::javaTimeMillis();
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jlong max_interval = (jlong)MinCodeCacheFlushingInterval * (jlong)1000;
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jlong curr_interval = now - _last_was_full;
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if ((!CodeCache::needs_flushing()) && (curr_interval > max_interval)) {
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CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
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set_was_full(false);
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// Update the _last_was_full time so we can tell how fast the
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// code cache is filling up
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_last_was_full = os::javaTimeMillis();
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if (PrintMethodFlushing) {
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tty->print_cr("### sweeper: Live blobs:" UINT32_FORMAT "/Free code cache:" SIZE_FORMAT " bytes, restarting compiler",
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CodeCache::nof_blobs(), CodeCache::unallocated_capacity());
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}
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if (LogCompilation && (xtty != NULL)) {
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ttyLocker ttyl;
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xtty->begin_elem("restart_compiler live_blobs='" UINT32_FORMAT "' free_code_cache='" SIZE_FORMAT "'",
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CodeCache::nof_blobs(), CodeCache::unallocated_capacity());
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xtty->stamp();
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xtty->end_elem();
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}
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}
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}
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}
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1
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}
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void NMethodSweeper::process_nmethod(nmethod *nm) {
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// Skip methods that are currently referenced by the VM
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if (nm->is_locked_by_vm()) {
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// But still remember to clean-up inline caches for alive nmethods
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if (nm->is_alive()) {
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// Clean-up all inline caches that points to zombie/non-reentrant methods
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nm->cleanup_inline_caches();
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} else {
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_locked_seen++;
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}
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return;
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}
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if (nm->is_zombie()) {
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// If it is first time, we see nmethod then we mark it. Otherwise,
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// we reclame it. When we have seen a zombie method twice, we know that
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// there are no inline caches that referes to it.
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if (nm->is_marked_for_reclamation()) {
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assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
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if (PrintMethodFlushing && Verbose) {
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tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);
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}
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nm->flush();
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} else {
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if (PrintMethodFlushing && Verbose) {
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tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
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}
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nm->mark_for_reclamation();
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_rescan = true;
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}
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} else if (nm->is_not_entrant()) {
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// If there is no current activations of this method on the
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// stack we can safely convert it to a zombie method
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if (nm->can_not_entrant_be_converted()) {
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if (PrintMethodFlushing && Verbose) {
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tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);
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}
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nm->make_zombie();
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_rescan = true;
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} else {
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// Still alive, clean up its inline caches
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nm->cleanup_inline_caches();
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// we coudn't transition this nmethod so don't immediately
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// request a rescan. If this method stays on the stack for a
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// long time we don't want to keep rescanning at every safepoint.
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_not_entrant_seen_on_stack++;
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}
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} else if (nm->is_unloaded()) {
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// Unloaded code, just make it a zombie
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if (PrintMethodFlushing && Verbose)
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tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);
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if (nm->is_osr_method()) {
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// No inline caches will ever point to osr methods, so we can just remove it
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nm->flush();
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} else {
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nm->make_zombie();
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_rescan = true;
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}
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} else {
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assert(nm->is_alive(), "should be alive");
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if (UseCodeCacheFlushing) {
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if ((nm->method()->code() != nm) && !(nm->is_locked_by_vm()) && !(nm->is_osr_method()) &&
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(_traversals > _was_full_traversal+2) && (((uint)nm->compile_id()) < _highest_marked) &&
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CodeCache::needs_flushing()) {
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// This method has not been called since the forced cleanup happened
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nm->make_not_entrant();
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}
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}
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// Clean-up all inline caches that points to zombie/non-reentrant methods
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nm->cleanup_inline_caches();
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}
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}
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// Code cache unloading: when compilers notice the code cache is getting full,
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// they will call a vm op that comes here. This code attempts to speculatively
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// unload the oldest half of the nmethods (based on the compile job id) by
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// saving the old code in a list in the CodeCache. Then
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// execution resumes. If a method so marked is not called by the second
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// safepoint from the current one, the nmethod will be marked non-entrant and
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// got rid of by normal sweeping. If the method is called, the methodOop's
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// _code field is restored and the methodOop/nmethod
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// go back to their normal state.
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void NMethodSweeper::handle_full_code_cache(bool is_full) {
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// Only the first one to notice can advise us to start early cleaning
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if (!is_full){
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jint old = Atomic::cmpxchg( 1, &_advise_to_sweep, 0 );
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if (old != 0) {
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return;
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}
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}
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if (is_full) {
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// Since code cache is full, immediately stop new compiles
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bool did_set = CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation);
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if (!did_set) {
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// only the first to notice can start the cleaning,
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// others will go back and block
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return;
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}
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set_was_full(true);
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// If we run out within MinCodeCacheFlushingInterval of the last unload time, give up
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jlong now = os::javaTimeMillis();
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jlong max_interval = (jlong)MinCodeCacheFlushingInterval * (jlong)1000;
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jlong curr_interval = now - _last_was_full;
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if (curr_interval < max_interval) {
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_rescan = true;
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if (PrintMethodFlushing) {
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tty->print_cr("### handle full too often, turning off compiler");
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}
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if (LogCompilation && (xtty != NULL)) {
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ttyLocker ttyl;
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xtty->begin_elem("disable_compiler flushing_interval='" UINT64_FORMAT "' live_blobs='" UINT32_FORMAT "' free_code_cache='" SIZE_FORMAT "'",
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curr_interval/1000, CodeCache::nof_blobs(), CodeCache::unallocated_capacity());
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xtty->stamp();
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xtty->end_elem();
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}
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return;
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}
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}
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VM_HandleFullCodeCache op(is_full);
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VMThread::execute(&op);
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// rescan again as soon as possible
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_rescan = true;
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}
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void NMethodSweeper::speculative_disconnect_nmethods(bool is_full) {
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// If there was a race in detecting full code cache, only run
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// one vm op for it or keep the compiler shut off
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debug_only(jlong start = os::javaTimeMillis();)
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if ((!was_full()) && (is_full)) {
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if (!CodeCache::needs_flushing()) {
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if (PrintMethodFlushing) {
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tty->print_cr("### sweeper: Live blobs:" UINT32_FORMAT "/Free code cache:" SIZE_FORMAT " bytes, restarting compiler",
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CodeCache::nof_blobs(), CodeCache::unallocated_capacity());
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}
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if (LogCompilation && (xtty != NULL)) {
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ttyLocker ttyl;
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xtty->begin_elem("restart_compiler live_blobs='" UINT32_FORMAT "' free_code_cache='" SIZE_FORMAT "'",
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CodeCache::nof_blobs(), CodeCache::unallocated_capacity());
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xtty->stamp();
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xtty->end_elem();
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}
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CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
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return;
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}
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}
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// Traverse the code cache trying to dump the oldest nmethods
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uint curr_max_comp_id = CompileBroker::get_compilation_id();
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uint flush_target = ((curr_max_comp_id - _highest_marked) >> 1) + _highest_marked;
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if (PrintMethodFlushing && Verbose) {
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tty->print_cr("### Cleaning code cache: Live blobs:" UINT32_FORMAT "/Free code cache:" SIZE_FORMAT " bytes",
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318 |
CodeCache::nof_blobs(), CodeCache::unallocated_capacity());
|
|
|
319 |
}
|
|
|
320 |
if (LogCompilation && (xtty != NULL)) {
|
|
|
321 |
ttyLocker ttyl;
|
|
|
322 |
xtty->begin_elem("start_cleaning_code_cache live_blobs='" UINT32_FORMAT "' free_code_cache='" SIZE_FORMAT "'",
|
|
|
323 |
CodeCache::nof_blobs(), CodeCache::unallocated_capacity());
|
|
|
324 |
xtty->stamp();
|
|
|
325 |
xtty->end_elem();
|
|
|
326 |
}
|
|
|
327 |
|
|
|
328 |
nmethod* nm = CodeCache::alive_nmethod(CodeCache::first());
|
|
|
329 |
jint disconnected = 0;
|
|
|
330 |
jint made_not_entrant = 0;
|
|
|
331 |
while ((nm != NULL)){
|
|
|
332 |
uint curr_comp_id = nm->compile_id();
|
|
|
333 |
|
|
|
334 |
// OSR methods cannot be flushed like this. Also, don't flush native methods
|
|
|
335 |
// since they are part of the JDK in most cases
|
|
|
336 |
if (nm->is_in_use() && (!nm->is_osr_method()) && (!nm->is_locked_by_vm()) &&
|
|
|
337 |
(!nm->is_native_method()) && ((curr_comp_id < flush_target))) {
|
|
|
338 |
|
|
|
339 |
if ((nm->method()->code() == nm)) {
|
|
|
340 |
// This method has not been previously considered for
|
|
|
341 |
// unloading or it was restored already
|
|
|
342 |
CodeCache::speculatively_disconnect(nm);
|
|
|
343 |
disconnected++;
|
|
|
344 |
} else if (nm->is_speculatively_disconnected()) {
|
|
|
345 |
// This method was previously considered for preemptive unloading and was not called since then
|
|
|
346 |
nm->method()->invocation_counter()->decay();
|
|
|
347 |
nm->method()->backedge_counter()->decay();
|
|
|
348 |
nm->make_not_entrant();
|
|
|
349 |
made_not_entrant++;
|
|
|
350 |
}
|
|
|
351 |
|
|
|
352 |
if (curr_comp_id > _highest_marked) {
|
|
|
353 |
_highest_marked = curr_comp_id;
|
|
|
354 |
}
|
|
|
355 |
}
|
|
|
356 |
nm = CodeCache::alive_nmethod(CodeCache::next(nm));
|
|
|
357 |
}
|
|
|
358 |
|
|
|
359 |
if (LogCompilation && (xtty != NULL)) {
|
|
|
360 |
ttyLocker ttyl;
|
|
|
361 |
xtty->begin_elem("stop_cleaning_code_cache disconnected='" UINT32_FORMAT "' made_not_entrant='" UINT32_FORMAT "' live_blobs='" UINT32_FORMAT "' free_code_cache='" SIZE_FORMAT "'",
|
|
|
362 |
disconnected, made_not_entrant, CodeCache::nof_blobs(), CodeCache::unallocated_capacity());
|
|
|
363 |
xtty->stamp();
|
|
|
364 |
xtty->end_elem();
|
|
|
365 |
}
|
|
|
366 |
|
|
|
367 |
// Shut off compiler. Sweeper will run exiting from this safepoint
|
|
|
368 |
// and turn it back on if it clears enough space
|
|
|
369 |
if (was_full()) {
|
|
|
370 |
_last_was_full = os::javaTimeMillis();
|
|
|
371 |
CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation);
|
|
|
372 |
}
|
|
|
373 |
|
|
|
374 |
// After two more traversals the sweeper will get rid of unrestored nmethods
|
|
|
375 |
_was_full_traversal = _traversals;
|
|
|
376 |
#ifdef ASSERT
|
|
|
377 |
jlong end = os::javaTimeMillis();
|
|
|
378 |
if(PrintMethodFlushing && Verbose) {
|
|
|
379 |
tty->print_cr("### sweeper: unload time: " INT64_FORMAT, end-start);
|
|
|
380 |
}
|
|
|
381 |
#endif
|
|
|
382 |
}
|