| /* |
| * 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(); |
| } |
| } |