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 /*

  * Copyright (c) 1997, 2010, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.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

 nmethod*  NMethodSweeper::_current = NULL;   // Current nmethod

 int       NMethodSweeper::_seen = 0 ;        // No. of nmethods we have currently processed in current pass of CodeCache

 volatile int NMethodSweeper::_invocations = 0;   // No. of invocations left until we are completed with this pass

 volatile int NMethodSweeper::_sweep_started = 0; // Whether a sweep is in progress.

 jint      NMethodSweeper::_locked_seen = 0;

 jint      NMethodSweeper::_not_entrant_seen_on_stack = 0;

 bool      NMethodSweeper::_rescan = false;

 bool      NMethodSweeper::_do_sweep = false;

 bool      NMethodSweeper::_was_full = false;

 jint      NMethodSweeper::_advise_to_sweep = 0;

 jlong     NMethodSweeper::_last_was_full = 0;

 uint      NMethodSweeper::_highest_marked = 0;

 long      NMethodSweeper::_was_full_traversal = 0;

 class MarkActivationClosure: public CodeBlobClosure {

 public:

   virtual void do_code_blob(CodeBlob* cb) {

     // If we see an activation belonging to a non_entrant nmethod, we mark it.

     if (cb->is_nmethod() && ((nmethod*)cb)->is_not_entrant()) {

       ((nmethod*)cb)->mark_as_seen_on_stack();

     }

   }

 };

 static MarkActivationClosure mark_activation_closure;

 void NMethodSweeper::scan_stacks() {

   assert(SafepointSynchronize::is_at_safepoint(), "must be executed at a safepoint");

   if (!MethodFlushing) return;

   _do_sweep = true;

   // 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 UseCodeCacheFlushing is on and

   // code cache flushing is in progress, don't skip sweeping to help make progress

   // clearing space in the code cache.

   if ((_current == NULL && !_rescan) && !(UseCodeCacheFlushing && !CompileBroker::should_compile_new_jobs())) {

     _do_sweep = false;

     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_nmethod();

     _traversals  += 1;

     if (PrintMethodFlushing) {

       tty->print_cr("### Sweep: stack traversal %d", _traversals);

     }

     Threads::nmethods_do(&mark_activation_closure);

     // reset the flags since we started a scan from the beginning.

     _rescan = false;

     _locked_seen = 0;

     _not_entrant_seen_on_stack = 0;

   }

   if (UseCodeCacheFlushing) {

     if (!CodeCache::needs_flushing()) {

       // scan_stacks() runs during a safepoint, no race with setters

       _advise_to_sweep = 0;

     }

     if (was_full()) {

       // There was some progress so attempt to restart the compiler

       jlong now           = os::javaTimeMillis();

       jlong max_interval  = (jlong)MinCodeCacheFlushingInterval * (jlong)1000;

       jlong curr_interval = now - _last_was_full;

       if ((!CodeCache::needs_flushing()) && (curr_interval > max_interval)) {

         CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);

         set_was_full(false);

         // Update the _last_was_full time so we can tell how fast the

         // code cache is filling up

         _last_was_full = os::javaTimeMillis();

         log_sweep("restart_compiler");

       }

     }

   }

 }

 void NMethodSweeper::possibly_sweep() {

   assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");

   if ((!MethodFlushing) || (!_do_sweep)) return;

   if (_invocations > 0) {

     // Only one thread at a time will sweep

     jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );

     if (old != 0) {

       return;

     }

     if (_invocations > 0) {

       sweep_code_cache();

       _invocations--;

     }

     _sweep_started = 0;

   }

 }

 void NMethodSweeper::sweep_code_cache() {

 #ifdef ASSERT

   jlong sweep_start;

   if (PrintMethodFlushing) {

     sweep_start = os::javaTimeMillis();

   }

 #endif

   if (PrintMethodFlushing && Verbose) {

     tty->print_cr("### Sweep at %d out of %d. Invocations left: %d", _seen, CodeCache::nof_nmethods(), _invocations);

   }

   // We want to visit all nmethods after NmethodSweepFraction

   // invocations so divide the remaining number of nmethods by the

   // remaining number of invocations.  This is only an estimate since

   // the number of nmethods changes during the sweep so the final

   // stage must iterate until it there are no more nmethods.

   int todo = (CodeCache::nof_nmethods() - _seen) / _invocations;

   assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");

   assert(!CodeCache_lock->owned_by_self(), "just checking");

   {

     MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);

     // The last invocation iterates until there are no more nmethods

     for (int i = 0; (i < todo || _invocations == 1) && _current != NULL; i++) {

       // Since we will give up the CodeCache_lock, always skip ahead

       // to the next nmethod.  Other blobs can be deleted by other

       // threads but nmethods are only reclaimed by the sweeper.

       nmethod* next = CodeCache::next_nmethod(_current);

       // Now ready to process nmethod and give up CodeCache_lock

       {

         MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);

         process_nmethod(_current);

       }

       _seen++;

       _current = next;

     }

   }

   assert(_invocations > 1 || _current == NULL, "must have scanned the whole cache");

   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");

     }

   }

 #ifdef ASSERT

   if(PrintMethodFlushing) {

     jlong sweep_end             = os::javaTimeMillis();

     tty->print_cr("### sweeper:      sweep time(%d): " INT64_FORMAT, _invocations, sweep_end - sweep_start);

   }

 #endif

   if (_invocations == 1) {

     log_sweep("finished");

   }

 }

 void NMethodSweeper::process_nmethod(nmethod *nm) {

   assert(!CodeCache_lock->owned_by_self(), "just checking");

   // 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

       MutexLocker cl(CompiledIC_lock);

       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 refer to it.

     if (nm->is_marked_for_reclamation()) {

       assert(!nm->is_locked_by_vm(), "must not flush locked nmethods");

       if (PrintMethodFlushing && Verbose) {

         tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (marked for reclamation) being flushed", nm->compile_id(), nm);

       }

       MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);

       nm->flush();

     } else {

       if (PrintMethodFlushing && Verbose) {

         tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);

       }

       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()) {

       if (PrintMethodFlushing && Verbose) {

         tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (not entrant) being made zombie", nm->compile_id(), nm);

       }

       nm->make_zombie();

       _rescan = true;

     } else {

       // Still alive, clean up its inline caches

       MutexLocker cl(CompiledIC_lock);

       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 the code cache.

       _not_entrant_seen_on_stack++;

     }

   } else if (nm->is_unloaded()) {

     // Unloaded code, just make it a zombie

     if (PrintMethodFlushing && Verbose)

       tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (unloaded) being made zombie", nm->compile_id(), nm);

     if (nm->is_osr_method()) {

       // No inline caches will ever point to osr methods, so we can just remove it

       MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);

       nm->flush();

     } else {

       nm->make_zombie();

       _rescan = true;

     }

   } else {

     assert(nm->is_alive(), "should be alive");

     if (UseCodeCacheFlushing) {

       if ((nm->method()->code() != nm) && !(nm->is_locked_by_vm()) && !(nm->is_osr_method()) &&

           (_traversals > _was_full_traversal+2) && (((uint)nm->compile_id()) < _highest_marked) &&

           CodeCache::needs_flushing()) {

         // This method has not been called since the forced cleanup happened

         nm->make_not_entrant();

       }

     }

     // Clean-up all inline caches that points to zombie/non-reentrant methods

     MutexLocker cl(CompiledIC_lock);

     nm->cleanup_inline_caches();

   }

 }

 // Code cache unloading: when compilers notice the code cache is getting full,

 // they will call a vm op that comes here. This code attempts to speculatively

 // unload the oldest half of the nmethods (based on the compile job id) by

 // saving the old code in a list in the CodeCache. Then

 // execution resumes. If a method so marked is not called by the second sweeper

 // stack traversal after the current one, the nmethod will be marked non-entrant and

 // got rid of by normal sweeping. If the method is called, the methodOop's

 // _code field is restored and the methodOop/nmethod

 // go back to their normal state.

 void NMethodSweeper::handle_full_code_cache(bool is_full) {

   // Only the first one to notice can advise us to start early cleaning

   if (!is_full){

     jint old = Atomic::cmpxchg( 1, &_advise_to_sweep, 0 );

     if (old != 0) {

       return;

     }

   }

   if (is_full) {

     // Since code cache is full, immediately stop new compiles

     bool did_set = CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation);

     if (!did_set) {

       // only the first to notice can start the cleaning,

       // others will go back and block

       return;

     }

     set_was_full(true);

     // If we run out within MinCodeCacheFlushingInterval of the last unload time, give up

     jlong now = os::javaTimeMillis();

     jlong max_interval = (jlong)MinCodeCacheFlushingInterval * (jlong)1000;

     jlong curr_interval = now - _last_was_full;

     if (curr_interval < max_interval) {

       _rescan = true;

       log_sweep("disable_compiler", "flushing_interval='" UINT64_FORMAT "'",

                            curr_interval/1000);

       return;

     }

   }

   VM_HandleFullCodeCache op(is_full);

   VMThread::execute(&op);

   // rescan again as soon as possible

   _rescan = true;

 }

 void NMethodSweeper::speculative_disconnect_nmethods(bool is_full) {

   // If there was a race in detecting full code cache, only run

   // one vm op for it or keep the compiler shut off

   debug_only(jlong start = os::javaTimeMillis();)

   if ((!was_full()) && (is_full)) {

     if (!CodeCache::needs_flushing()) {

       log_sweep("restart_compiler");

       CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);

       return;

     }

   }

   // Traverse the code cache trying to dump the oldest nmethods

   uint curr_max_comp_id = CompileBroker::get_compilation_id();

   uint flush_target = ((curr_max_comp_id - _highest_marked) >> 1) + _highest_marked;

   log_sweep("start_cleaning");

   nmethod* nm = CodeCache::alive_nmethod(CodeCache::first());

   jint disconnected = 0;

   jint made_not_entrant  = 0;

   while ((nm != NULL)){

     uint curr_comp_id = nm->compile_id();

     // OSR methods cannot be flushed like this. Also, don't flush native methods

     // since they are part of the JDK in most cases

     if (nm->is_in_use() && (!nm->is_osr_method()) && (!nm->is_locked_by_vm()) &&

         (!nm->is_native_method()) && ((curr_comp_id < flush_target))) {

       if ((nm->method()->code() == nm)) {

         // This method has not been previously considered for

         // unloading or it was restored already

         CodeCache::speculatively_disconnect(nm);

         disconnected++;

       } else if (nm->is_speculatively_disconnected()) {

         // This method was previously considered for preemptive unloading and was not called since then

         nm->method()->invocation_counter()->decay();

         nm->method()->backedge_counter()->decay();

         nm->make_not_entrant();

         made_not_entrant++;

       }

       if (curr_comp_id > _highest_marked) {

         _highest_marked = curr_comp_id;

       }

     }

     nm = CodeCache::alive_nmethod(CodeCache::next(nm));

   }

   log_sweep("stop_cleaning",

                        "disconnected='" UINT32_FORMAT "' made_not_entrant='" UINT32_FORMAT "'",

                        disconnected, made_not_entrant);

   // Shut off compiler. Sweeper will start over with a new stack scan and

   // traversal cycle and turn it back on if it clears enough space.

   if (was_full()) {

     _last_was_full = os::javaTimeMillis();

     CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation);

   }

   // After two more traversals the sweeper will get rid of unrestored nmethods

   _was_full_traversal = _traversals;

 #ifdef ASSERT

   jlong end = os::javaTimeMillis();

   if(PrintMethodFlushing && Verbose) {

     tty->print_cr("### sweeper: unload time: " INT64_FORMAT, end-start);

   }

 #endif

 }

 // Print out some state information about the current sweep and the

 // state of the code cache if it's requested.

 void NMethodSweeper::log_sweep(const char* msg, const char* format, ...) {

   if (PrintMethodFlushing) {

     ttyLocker ttyl;

     tty->print("### sweeper: %s ", msg);

     if (format != NULL) {

       va_list ap;

       va_start(ap, format);

       tty->vprint(format, ap);

       va_end(ap);

     }

     tty->print_cr(" total_blobs='" UINT32_FORMAT "' nmethods='" UINT32_FORMAT "'"

                   " adapters='" UINT32_FORMAT "' free_code_cache='" SIZE_FORMAT "'",

                   CodeCache::nof_blobs(), CodeCache::nof_nmethods(), CodeCache::nof_adapters(), CodeCache::unallocated_capacity());

   }

   if (LogCompilation && (xtty != NULL)) {

     ttyLocker ttyl;

     xtty->begin_elem("sweeper state='%s' traversals='" INTX_FORMAT "' ", msg, (intx)traversal_count());

     if (format != NULL) {

       va_list ap;

       va_start(ap, format);

       xtty->vprint(format, ap);

       va_end(ap);

     }

     xtty->print(" total_blobs='" UINT32_FORMAT "' nmethods='" UINT32_FORMAT "'"

                 " adapters='" UINT32_FORMAT "' free_code_cache='" SIZE_FORMAT "'",

                 CodeCache::nof_blobs(), CodeCache::nof_nmethods(), CodeCache::nof_adapters(), CodeCache::unallocated_capacity());

     xtty->stamp();

     xtty->end_elem();

   }

 }