duke@435: /*
duke@435:  * Copyright 1997-2005 Sun Microsystems, Inc.  All Rights Reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
duke@435:  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@435:  * CA 95054 USA or visit www.sun.com if you need additional information or
duke@435:  * have any questions.
duke@435:  *
duke@435:  */
duke@435: 
duke@435: # include "incls/_precompiled.incl"
duke@435: # include "incls/_sweeper.cpp.incl"
duke@435: 
duke@435: long      NMethodSweeper::_traversals = 0;   // No. of stack traversals performed
duke@435: CodeBlob* NMethodSweeper::_current = NULL;   // Current nmethod
duke@435: int       NMethodSweeper::_seen = 0 ;        // No. of blobs we have currently processed in current pass of CodeCache
duke@435: int       NMethodSweeper::_invocations = 0;  // No. of invocations left until we are completed with this pass
duke@435: 
duke@435: jint      NMethodSweeper::_locked_seen = 0;
duke@435: jint      NMethodSweeper::_not_entrant_seen_on_stack = 0;
duke@435: bool      NMethodSweeper::_rescan = false;
duke@435: 
duke@435: void NMethodSweeper::sweep() {
duke@435:   assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
duke@435:   if (!MethodFlushing) return;
duke@435: 
duke@435:   // No need to synchronize access, since this is always executed at a
duke@435:   // safepoint.  If we aren't in the middle of scan and a rescan
duke@435:   // hasn't been requested then just return.
duke@435:   if (_current == NULL && !_rescan) return;
duke@435: 
duke@435:   // Make sure CompiledIC_lock in unlocked, since we might update some
duke@435:   // inline caches. If it is, we just bail-out and try later.
duke@435:   if (CompiledIC_lock->is_locked() || Patching_lock->is_locked()) return;
duke@435: 
duke@435:   // Check for restart
duke@435:   assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");
duke@435:   if (_current == NULL) {
duke@435:     _seen        = 0;
duke@435:     _invocations = NmethodSweepFraction;
duke@435:     _current     = CodeCache::first();
duke@435:     _traversals  += 1;
duke@435:     if (PrintMethodFlushing) {
duke@435:       tty->print_cr("### Sweep: stack traversal %d", _traversals);
duke@435:     }
duke@435:     Threads::nmethods_do();
duke@435: 
duke@435:     // reset the flags since we started a scan from the beginning.
duke@435:     _rescan = false;
duke@435:     _locked_seen = 0;
duke@435:     _not_entrant_seen_on_stack = 0;
duke@435:   }
duke@435: 
duke@435:   if (PrintMethodFlushing && Verbose) {
duke@435:     tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_blobs(), _invocations);
duke@435:   }
duke@435: 
duke@435:   // We want to visit all nmethods after NmethodSweepFraction invocations.
duke@435:   // If invocation is 1 we do the rest
duke@435:   int todo = CodeCache::nof_blobs();
duke@435:   if (_invocations != 1) {
duke@435:     todo = (CodeCache::nof_blobs() - _seen) / _invocations;
duke@435:     _invocations--;
duke@435:   }
duke@435: 
duke@435:   for(int i = 0; i < todo && _current != NULL; i++) {
duke@435:     CodeBlob* next = CodeCache::next(_current); // Read next before we potentially delete current
duke@435:     if (_current->is_nmethod()) {
duke@435:       process_nmethod((nmethod *)_current);
duke@435:     }
duke@435:     _seen++;
duke@435:     _current = next;
duke@435:   }
duke@435:   // Because we could stop on a codeBlob other than an nmethod we skip forward
duke@435:   // to the next nmethod (if any). codeBlobs other than nmethods can be freed
duke@435:   // async to us and make _current invalid while we sleep.
duke@435:   while (_current != NULL && !_current->is_nmethod()) {
duke@435:     _current = CodeCache::next(_current);
duke@435:   }
duke@435: 
duke@435:   if (_current == NULL && !_rescan && (_locked_seen || _not_entrant_seen_on_stack)) {
duke@435:     // we've completed a scan without making progress but there were
duke@435:     // nmethods we were unable to process either because they were
duke@435:     // locked or were still on stack.  We don't have to aggresively
duke@435:     // clean them up so just stop scanning.  We could scan once more
duke@435:     // but that complicates the control logic and it's unlikely to
duke@435:     // matter much.
duke@435:     if (PrintMethodFlushing) {
duke@435:       tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
duke@435:     }
duke@435:   }
duke@435: }
duke@435: 
duke@435: 
duke@435: void NMethodSweeper::process_nmethod(nmethod *nm) {
duke@435:   // Skip methods that are currently referenced by the VM
duke@435:   if (nm->is_locked_by_vm()) {
duke@435:     // But still remember to clean-up inline caches for alive nmethods
duke@435:     if (nm->is_alive()) {
duke@435:       // Clean-up all inline caches that points to zombie/non-reentrant methods
duke@435:       nm->cleanup_inline_caches();
duke@435:     } else {
duke@435:       _locked_seen++;
duke@435:     }
duke@435:     return;
duke@435:   }
duke@435: 
duke@435:   if (nm->is_zombie()) {
duke@435:     // If it is first time, we see nmethod then we mark it. Otherwise,
duke@435:     // we reclame it. When we have seen a zombie method twice, we know that
duke@435:     // there are no inline caches that referes to it.
duke@435:     if (nm->is_marked_for_reclamation()) {
duke@435:       assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
duke@435:       nm->flush();
duke@435:     } else {
duke@435:       nm->mark_for_reclamation();
duke@435:       _rescan = true;
duke@435:     }
duke@435:   } else if (nm->is_not_entrant()) {
duke@435:     // If there is no current activations of this method on the
duke@435:     // stack we can safely convert it to a zombie method
duke@435:     if (nm->can_not_entrant_be_converted()) {
duke@435:       nm->make_zombie();
duke@435:       _rescan = true;
duke@435:     } else {
duke@435:       // Still alive, clean up its inline caches
duke@435:       nm->cleanup_inline_caches();
duke@435:       // we coudn't transition this nmethod so don't immediately
duke@435:       // request a rescan.  If this method stays on the stack for a
duke@435:       // long time we don't want to keep rescanning at every safepoint.
duke@435:       _not_entrant_seen_on_stack++;
duke@435:     }
duke@435:   } else if (nm->is_unloaded()) {
duke@435:     // Unloaded code, just make it a zombie
duke@435:     if (nm->is_osr_only_method()) {
duke@435:       // No inline caches will ever point to osr methods, so we can just remove it
duke@435:       nm->flush();
duke@435:     } else {
duke@435:       nm->make_zombie();
duke@435:       _rescan = true;
duke@435:     }
duke@435:   } else {
duke@435:     assert(nm->is_alive(), "should be alive");
duke@435:     // Clean-up all inline caches that points to zombie/non-reentrant methods
duke@435:     nm->cleanup_inline_caches();
duke@435:   }
duke@435: }