duke@435: /*
never@1999:  * Copyright (c) 1997, 2010, Oracle and/or its affiliates. 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:  *
trims@1907:  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
trims@1907:  * or visit www.oracle.com if you need additional information or have any
trims@1907:  * questions.
duke@435:  *
duke@435:  */
duke@435: 
stefank@2314: #include "precompiled.hpp"
stefank@2314: #include "code/codeCache.hpp"
stefank@2314: #include "code/nmethod.hpp"
stefank@2314: #include "compiler/compileBroker.hpp"
stefank@2314: #include "memory/resourceArea.hpp"
stefank@2314: #include "oops/methodOop.hpp"
stefank@2314: #include "runtime/atomic.hpp"
stefank@2314: #include "runtime/compilationPolicy.hpp"
stefank@2314: #include "runtime/mutexLocker.hpp"
stefank@2314: #include "runtime/os.hpp"
stefank@2314: #include "runtime/sweeper.hpp"
stefank@2314: #include "runtime/vm_operations.hpp"
stefank@2314: #include "utilities/events.hpp"
stefank@2314: #include "utilities/xmlstream.hpp"
duke@435: 
duke@435: long      NMethodSweeper::_traversals = 0;   // No. of stack traversals performed
never@1970: nmethod*  NMethodSweeper::_current = NULL;   // Current nmethod
never@1999: int       NMethodSweeper::_seen = 0 ;        // No. of nmethods we have currently processed in current pass of CodeCache
never@1999: 
never@1999: volatile int NMethodSweeper::_invocations = 0;   // No. of invocations left until we are completed with this pass
never@1999: volatile int NMethodSweeper::_sweep_started = 0; // Whether a sweep is in progress.
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;
never@1893: bool      NMethodSweeper::_do_sweep = false;
kvn@1637: bool      NMethodSweeper::_was_full = false;
kvn@1637: jint      NMethodSweeper::_advise_to_sweep = 0;
kvn@1637: jlong     NMethodSweeper::_last_was_full = 0;
kvn@1637: uint      NMethodSweeper::_highest_marked = 0;
kvn@1637: long      NMethodSweeper::_was_full_traversal = 0;
duke@435: 
jrose@1424: class MarkActivationClosure: public CodeBlobClosure {
jrose@1424: public:
jrose@1424:   virtual void do_code_blob(CodeBlob* cb) {
jrose@1424:     // If we see an activation belonging to a non_entrant nmethod, we mark it.
jrose@1424:     if (cb->is_nmethod() && ((nmethod*)cb)->is_not_entrant()) {
jrose@1424:       ((nmethod*)cb)->mark_as_seen_on_stack();
jrose@1424:     }
jrose@1424:   }
jrose@1424: };
jrose@1424: static MarkActivationClosure mark_activation_closure;
jrose@1424: 
never@1893: void NMethodSweeper::scan_stacks() {
duke@435:   assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");
duke@435:   if (!MethodFlushing) return;
never@1893:   _do_sweep = true;
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
never@1893:   // hasn't been requested then just return. If UseCodeCacheFlushing is on and
never@1893:   // code cache flushing is in progress, don't skip sweeping to help make progress
never@1893:   // clearing space in the code cache.
never@1893:   if ((_current == NULL && !_rescan) && !(UseCodeCacheFlushing && !CompileBroker::should_compile_new_jobs())) {
never@1893:     _do_sweep = false;
never@1893:     return;
never@1893:   }
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;
never@1893:     _current     = CodeCache::first_nmethod();
duke@435:     _traversals  += 1;
duke@435:     if (PrintMethodFlushing) {
duke@435:       tty->print_cr("### Sweep: stack traversal %d", _traversals);
duke@435:     }
jrose@1424:     Threads::nmethods_do(&mark_activation_closure);
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: 
kvn@1637:   if (UseCodeCacheFlushing) {
kvn@1637:     if (!CodeCache::needs_flushing()) {
never@1893:       // scan_stacks() runs during a safepoint, no race with setters
kvn@1637:       _advise_to_sweep = 0;
kvn@1637:     }
kvn@1637: 
kvn@1637:     if (was_full()) {
kvn@1637:       // There was some progress so attempt to restart the compiler
kvn@1637:       jlong now           = os::javaTimeMillis();
kvn@1637:       jlong max_interval  = (jlong)MinCodeCacheFlushingInterval * (jlong)1000;
kvn@1637:       jlong curr_interval = now - _last_was_full;
kvn@1637:       if ((!CodeCache::needs_flushing()) && (curr_interval > max_interval)) {
kvn@1637:         CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
kvn@1637:         set_was_full(false);
kvn@1637: 
kvn@1637:         // Update the _last_was_full time so we can tell how fast the
kvn@1637:         // code cache is filling up
kvn@1637:         _last_was_full = os::javaTimeMillis();
kvn@1637: 
never@1999:         log_sweep("restart_compiler");
kvn@1637:       }
kvn@1637:     }
kvn@1637:   }
duke@435: }
duke@435: 
never@1893: void NMethodSweeper::possibly_sweep() {
never@1999:   assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
never@1893:   if ((!MethodFlushing) || (!_do_sweep)) return;
never@1893: 
never@1893:   if (_invocations > 0) {
never@1893:     // Only one thread at a time will sweep
never@1893:     jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );
never@1893:     if (old != 0) {
never@1893:       return;
never@1893:     }
never@1999:     if (_invocations > 0) {
never@1999:       sweep_code_cache();
never@1999:       _invocations--;
never@1999:     }
never@1999:     _sweep_started = 0;
never@1893:   }
never@1893: }
never@1893: 
never@1893: void NMethodSweeper::sweep_code_cache() {
never@1893: #ifdef ASSERT
never@1893:   jlong sweep_start;
never@1999:   if (PrintMethodFlushing) {
never@1893:     sweep_start = os::javaTimeMillis();
never@1893:   }
never@1893: #endif
never@1893:   if (PrintMethodFlushing && Verbose) {
never@1999:     tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _invocations);
never@1893:   }
never@1893: 
never@1999:   // We want to visit all nmethods after NmethodSweepFraction
never@1999:   // invocations so divide the remaining number of nmethods by the
never@1999:   // remaining number of invocations.  This is only an estimate since
never@1999:   // the number of nmethods changes during the sweep so the final
never@1999:   // stage must iterate until it there are no more nmethods.
never@1999:   int todo = (CodeCache::nof_nmethods() - _seen) / _invocations;
never@1893: 
never@1893:   assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
never@1893:   assert(!CodeCache_lock->owned_by_self(), "just checking");
never@1893: 
never@1893:   {
never@1893:     MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
never@1893: 
never@1999:     // The last invocation iterates until there are no more nmethods
never@1999:     for (int i = 0; (i < todo || _invocations == 1) && _current != NULL; i++) {
never@1893: 
never@1999:       // Since we will give up the CodeCache_lock, always skip ahead
never@1999:       // to the next nmethod.  Other blobs can be deleted by other
never@1999:       // threads but nmethods are only reclaimed by the sweeper.
never@1970:       nmethod* next = CodeCache::next_nmethod(_current);
never@1893: 
never@1893:       // Now ready to process nmethod and give up CodeCache_lock
never@1893:       {
never@1893:         MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
never@1970:         process_nmethod(_current);
never@1893:       }
never@1893:       _seen++;
never@1893:       _current = next;
never@1893:     }
never@1893:   }
never@1893: 
never@1999:   assert(_invocations > 1 || _current == NULL, "must have scanned the whole cache");
never@1999: 
never@1893:   if (_current == NULL && !_rescan && (_locked_seen || _not_entrant_seen_on_stack)) {
never@1893:     // we've completed a scan without making progress but there were
never@1893:     // nmethods we were unable to process either because they were
never@1893:     // locked or were still on stack.  We don't have to aggresively
never@1893:     // clean them up so just stop scanning.  We could scan once more
never@1893:     // but that complicates the control logic and it's unlikely to
never@1893:     // matter much.
never@1893:     if (PrintMethodFlushing) {
never@1893:       tty->print_cr("### Couldn't make progress on some nmethods so stopping sweep");
never@1893:     }
never@1893:   }
never@1893: 
never@1893: #ifdef ASSERT
never@1893:   if(PrintMethodFlushing) {
never@1893:     jlong sweep_end             = os::javaTimeMillis();
never@1893:     tty->print_cr("### sweeper:      sweep time(%d): " INT64_FORMAT, _invocations, sweep_end - sweep_start);
never@1893:   }
never@1893: #endif
never@1999: 
never@1999:   if (_invocations == 1) {
never@1999:     log_sweep("finished");
never@1999:   }
never@1893: }
never@1893: 
duke@435: 
duke@435: void NMethodSweeper::process_nmethod(nmethod *nm) {
never@1893:   assert(!CodeCache_lock->owned_by_self(), "just checking");
never@1893: 
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
never@1893:       MutexLocker cl(CompiledIC_lock);
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
never@1999:     // there are no inline caches that refer to it.
duke@435:     if (nm->is_marked_for_reclamation()) {
duke@435:       assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");
ysr@1376:       if (PrintMethodFlushing && Verbose) {
kvn@1637:         tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);
ysr@1376:       }
never@1893:       MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
duke@435:       nm->flush();
duke@435:     } else {
ysr@1376:       if (PrintMethodFlushing && Verbose) {
kvn@1637:         tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
ysr@1376:       }
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()) {
ysr@1376:       if (PrintMethodFlushing && Verbose) {
kvn@1637:         tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);
ysr@1376:       }
duke@435:       nm->make_zombie();
duke@435:       _rescan = true;
duke@435:     } else {
duke@435:       // Still alive, clean up its inline caches
never@1893:       MutexLocker cl(CompiledIC_lock);
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
never@1893:       // long time we don't want to keep rescanning the code cache.
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
ysr@1376:     if (PrintMethodFlushing && Verbose)
kvn@1637:       tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);
ysr@1376:     if (nm->is_osr_method()) {
duke@435:       // No inline caches will ever point to osr methods, so we can just remove it
never@1893:       MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
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");
kvn@1637: 
kvn@1637:     if (UseCodeCacheFlushing) {
kvn@1637:       if ((nm->method()->code() != nm) && !(nm->is_locked_by_vm()) && !(nm->is_osr_method()) &&
kvn@1637:           (_traversals > _was_full_traversal+2) && (((uint)nm->compile_id()) < _highest_marked) &&
kvn@1637:           CodeCache::needs_flushing()) {
kvn@1637:         // This method has not been called since the forced cleanup happened
kvn@1637:         nm->make_not_entrant();
kvn@1637:       }
kvn@1637:     }
kvn@1637: 
duke@435:     // Clean-up all inline caches that points to zombie/non-reentrant methods
never@1893:     MutexLocker cl(CompiledIC_lock);
duke@435:     nm->cleanup_inline_caches();
duke@435:   }
duke@435: }
kvn@1637: 
kvn@1637: // Code cache unloading: when compilers notice the code cache is getting full,
kvn@1637: // they will call a vm op that comes here. This code attempts to speculatively
kvn@1637: // unload the oldest half of the nmethods (based on the compile job id) by
kvn@1637: // saving the old code in a list in the CodeCache. Then
never@1893: // execution resumes. If a method so marked is not called by the second sweeper
never@1893: // stack traversal after the current one, the nmethod will be marked non-entrant and
kvn@1637: // got rid of by normal sweeping. If the method is called, the methodOop's
kvn@1637: // _code field is restored and the methodOop/nmethod
kvn@1637: // go back to their normal state.
kvn@1637: void NMethodSweeper::handle_full_code_cache(bool is_full) {
kvn@1637:   // Only the first one to notice can advise us to start early cleaning
kvn@1637:   if (!is_full){
kvn@1637:     jint old = Atomic::cmpxchg( 1, &_advise_to_sweep, 0 );
kvn@1637:     if (old != 0) {
kvn@1637:       return;
kvn@1637:     }
kvn@1637:   }
kvn@1637: 
kvn@1637:   if (is_full) {
kvn@1637:     // Since code cache is full, immediately stop new compiles
kvn@1637:     bool did_set = CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation);
kvn@1637:     if (!did_set) {
kvn@1637:       // only the first to notice can start the cleaning,
kvn@1637:       // others will go back and block
kvn@1637:       return;
kvn@1637:     }
kvn@1637:     set_was_full(true);
kvn@1637: 
kvn@1637:     // If we run out within MinCodeCacheFlushingInterval of the last unload time, give up
kvn@1637:     jlong now = os::javaTimeMillis();
kvn@1637:     jlong max_interval = (jlong)MinCodeCacheFlushingInterval * (jlong)1000;
kvn@1637:     jlong curr_interval = now - _last_was_full;
kvn@1637:     if (curr_interval < max_interval) {
kvn@1637:       _rescan = true;
never@1999:       log_sweep("disable_compiler", "flushing_interval='" UINT64_FORMAT "'",
never@1999:                            curr_interval/1000);
kvn@1637:       return;
kvn@1637:     }
kvn@1637:   }
kvn@1637: 
kvn@1637:   VM_HandleFullCodeCache op(is_full);
kvn@1637:   VMThread::execute(&op);
kvn@1637: 
kvn@1637:   // rescan again as soon as possible
kvn@1637:   _rescan = true;
kvn@1637: }
kvn@1637: 
kvn@1637: void NMethodSweeper::speculative_disconnect_nmethods(bool is_full) {
kvn@1637:   // If there was a race in detecting full code cache, only run
kvn@1637:   // one vm op for it or keep the compiler shut off
kvn@1637: 
kvn@1637:   debug_only(jlong start = os::javaTimeMillis();)
kvn@1637: 
kvn@1637:   if ((!was_full()) && (is_full)) {
kvn@1637:     if (!CodeCache::needs_flushing()) {
never@1999:       log_sweep("restart_compiler");
kvn@1637:       CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
kvn@1637:       return;
kvn@1637:     }
kvn@1637:   }
kvn@1637: 
kvn@1637:   // Traverse the code cache trying to dump the oldest nmethods
kvn@1637:   uint curr_max_comp_id = CompileBroker::get_compilation_id();
kvn@1637:   uint flush_target = ((curr_max_comp_id - _highest_marked) >> 1) + _highest_marked;
never@1999:   log_sweep("start_cleaning");
kvn@1637: 
kvn@1637:   nmethod* nm = CodeCache::alive_nmethod(CodeCache::first());
kvn@1637:   jint disconnected = 0;
kvn@1637:   jint made_not_entrant  = 0;
kvn@1637:   while ((nm != NULL)){
kvn@1637:     uint curr_comp_id = nm->compile_id();
kvn@1637: 
kvn@1637:     // OSR methods cannot be flushed like this. Also, don't flush native methods
kvn@1637:     // since they are part of the JDK in most cases
kvn@1637:     if (nm->is_in_use() && (!nm->is_osr_method()) && (!nm->is_locked_by_vm()) &&
kvn@1637:         (!nm->is_native_method()) && ((curr_comp_id < flush_target))) {
kvn@1637: 
kvn@1637:       if ((nm->method()->code() == nm)) {
kvn@1637:         // This method has not been previously considered for
kvn@1637:         // unloading or it was restored already
kvn@1637:         CodeCache::speculatively_disconnect(nm);
kvn@1637:         disconnected++;
kvn@1637:       } else if (nm->is_speculatively_disconnected()) {
kvn@1637:         // This method was previously considered for preemptive unloading and was not called since then
iveresov@2138:         CompilationPolicy::policy()->delay_compilation(nm->method());
kvn@1637:         nm->make_not_entrant();
kvn@1637:         made_not_entrant++;
kvn@1637:       }
kvn@1637: 
kvn@1637:       if (curr_comp_id > _highest_marked) {
kvn@1637:         _highest_marked = curr_comp_id;
kvn@1637:       }
kvn@1637:     }
kvn@1637:     nm = CodeCache::alive_nmethod(CodeCache::next(nm));
kvn@1637:   }
kvn@1637: 
never@1999:   log_sweep("stop_cleaning",
never@1999:                        "disconnected='" UINT32_FORMAT "' made_not_entrant='" UINT32_FORMAT "'",
never@1999:                        disconnected, made_not_entrant);
kvn@1637: 
never@1893:   // Shut off compiler. Sweeper will start over with a new stack scan and
never@1893:   // traversal cycle and turn it back on if it clears enough space.
kvn@1637:   if (was_full()) {
kvn@1637:     _last_was_full = os::javaTimeMillis();
kvn@1637:     CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation);
kvn@1637:   }
kvn@1637: 
kvn@1637:   // After two more traversals the sweeper will get rid of unrestored nmethods
kvn@1637:   _was_full_traversal = _traversals;
kvn@1637: #ifdef ASSERT
kvn@1637:   jlong end = os::javaTimeMillis();
kvn@1637:   if(PrintMethodFlushing && Verbose) {
kvn@1637:     tty->print_cr("### sweeper: unload time: " INT64_FORMAT, end-start);
kvn@1637:   }
kvn@1637: #endif
kvn@1637: }
never@1999: 
never@1999: 
never@1999: // Print out some state information about the current sweep and the
never@1999: // state of the code cache if it's requested.
never@1999: void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {
never@1999:   if (PrintMethodFlushing) {
never@1999:     ttyLocker ttyl;
never@1999:     tty->print("### sweeper: %s ", msg);
never@1999:     if (format != NULL) {
never@1999:       va_list ap;
never@1999:       va_start(ap, format);
never@1999:       tty->vprint(format, ap);
never@1999:       va_end(ap);
never@1999:     }
never@1999:     tty->print_cr(" total_blobs='" UINT32_FORMAT "' nmethods='" UINT32_FORMAT "'"
never@1999:                   " adapters='" UINT32_FORMAT "' free_code_cache='" SIZE_FORMAT "'",
never@1999:                   CodeCache::nof_blobs(), CodeCache::nof_nmethods(), CodeCache::nof_adapters(), CodeCache::unallocated_capacity());
never@1999:   }
never@1999: 
never@1999:   if (LogCompilation && (xtty != NULL)) {
never@1999:     ttyLocker ttyl;
never@2001:     xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count());
never@1999:     if (format != NULL) {
never@1999:       va_list ap;
never@1999:       va_start(ap, format);
never@1999:       xtty->vprint(format, ap);
never@1999:       va_end(ap);
never@1999:     }
never@1999:     xtty->print(" total_blobs='" UINT32_FORMAT "' nmethods='" UINT32_FORMAT "'"
never@1999:                 " adapters='" UINT32_FORMAT "' free_code_cache='" SIZE_FORMAT "'",
never@1999:                 CodeCache::nof_blobs(), CodeCache::nof_nmethods(), CodeCache::nof_adapters(), CodeCache::unallocated_capacity());
never@1999:     xtty->stamp();
never@1999:     xtty->end_elem();
never@1999:   }
never@1999: }