Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 1997, 2013, 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 "precompiled.hpp"

 #include "code/codeCache.hpp"

 #include "code/compiledIC.hpp"

 #include "code/icBuffer.hpp"

 #include "code/nmethod.hpp"

 #include "compiler/compileBroker.hpp"

 #include "memory/resourceArea.hpp"

 #include "oops/method.hpp"

 #include "runtime/atomic.hpp"

 #include "runtime/compilationPolicy.hpp"

 #include "runtime/mutexLocker.hpp"

 #include "runtime/os.hpp"

 #include "runtime/sweeper.hpp"

 #include "runtime/vm_operations.hpp"

 #include "trace/tracing.hpp"

 #include "utilities/events.hpp"

 #include "utilities/ticks.inline.hpp"

 #include "utilities/xmlstream.hpp"

 #ifdef ASSERT

 #define SWEEP(nm) record_sweep(nm, __LINE__)

 // Sweeper logging code

 class SweeperRecord {

  public:

   int traversal;

   int invocation;

   int compile_id;

   long traversal_mark;

   int state;

   const char* kind;

   address vep;

   address uep;

   int line;

   void print() {

       tty->print_cr("traversal = %d invocation = %d compile_id = %d %s uep = " PTR_FORMAT " vep = "

                     PTR_FORMAT " state = %d traversal_mark %d line = %d",

                     traversal,

                     invocation,

                     compile_id,

                     kind == NULL ? "" : kind,

                     uep,

                     vep,

                     state,

                     traversal_mark,

                     line);

   }

 };

 static int _sweep_index = 0;

 static SweeperRecord* _records = NULL;

 void NMethodSweeper::report_events(int id, address entry) {

   if (_records != NULL) {

     for (int i = _sweep_index; i < SweeperLogEntries; i++) {

       if (_records[i].uep == entry ||

           _records[i].vep == entry ||

           _records[i].compile_id == id) {

         _records[i].print();

       }

     }

     for (int i = 0; i < _sweep_index; i++) {

       if (_records[i].uep == entry ||

           _records[i].vep == entry ||

           _records[i].compile_id == id) {

         _records[i].print();

       }

     }

   }

 }

 void NMethodSweeper::report_events() {

   if (_records != NULL) {

     for (int i = _sweep_index; i < SweeperLogEntries; i++) {

       // skip empty records

       if (_records[i].vep == NULL) continue;

       _records[i].print();

     }

     for (int i = 0; i < _sweep_index; i++) {

       // skip empty records

       if (_records[i].vep == NULL) continue;

       _records[i].print();

     }

   }

 }

 void NMethodSweeper::record_sweep(nmethod* nm, int line) {

   if (_records != NULL) {

     _records[_sweep_index].traversal = _traversals;

     _records[_sweep_index].traversal_mark = nm->_stack_traversal_mark;

     _records[_sweep_index].invocation = _sweep_fractions_left;

     _records[_sweep_index].compile_id = nm->compile_id();

     _records[_sweep_index].kind = nm->compile_kind();

     _records[_sweep_index].state = nm->_state;

     _records[_sweep_index].vep = nm->verified_entry_point();

     _records[_sweep_index].uep = nm->entry_point();

     _records[_sweep_index].line = line;

     _sweep_index = (_sweep_index + 1) % SweeperLogEntries;

   }

 }

 #else

 #define SWEEP(nm)

 #endif

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

 long     NMethodSweeper::_traversals                   = 0;    // Stack scan count, also sweep ID.

 long     NMethodSweeper::_time_counter                 = 0;    // Virtual time used to periodically invoke sweeper

 long     NMethodSweeper::_last_sweep                   = 0;    // Value of _time_counter when the last sweep happened

 int      NMethodSweeper::_seen                         = 0;    // Nof. nmethod we have currently processed in current pass of CodeCache

 int      NMethodSweeper::_flushed_count                = 0;    // Nof. nmethods flushed in current sweep

 int      NMethodSweeper::_zombified_count              = 0;    // Nof. nmethods made zombie in current sweep

 int      NMethodSweeper::_marked_for_reclamation_count = 0;    // Nof. nmethods marked for reclaim in current sweep

 volatile bool NMethodSweeper::_should_sweep            = true; // Indicates if we should invoke the sweeper

 volatile int  NMethodSweeper::_sweep_fractions_left    = 0;    // Nof. invocations left until we are completed with this pass

 volatile int  NMethodSweeper::_sweep_started           = 0;    // Flag to control conc sweeper

 volatile int  NMethodSweeper::_bytes_changed           = 0;    // Counts the total nmethod size if the nmethod changed from:

                                                                //   1) alive       -> not_entrant

                                                                //   2) not_entrant -> zombie

                                                                //   3) zombie      -> marked_for_reclamation

 int   NMethodSweeper::_total_nof_methods_reclaimed     = 0;    // Accumulated nof methods flushed

 Tickspan NMethodSweeper::_total_time_sweeping;                 // Accumulated time sweeping

 Tickspan NMethodSweeper::_total_time_this_sweep;               // Total time this sweep

 Tickspan NMethodSweeper::_peak_sweep_time;                     // Peak time for a full sweep

 Tickspan NMethodSweeper::_peak_sweep_fraction_time;            // Peak time sweeping one fraction

 int   NMethodSweeper::_hotness_counter_reset_val       = 0;

 class MarkActivationClosure: public CodeBlobClosure {

 public:

   virtual void do_code_blob(CodeBlob* cb) {

     if (cb->is_nmethod()) {

       nmethod* nm = (nmethod*)cb;

       nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());

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

       if (nm->is_not_entrant()) {

         nm->mark_as_seen_on_stack();

       }

     }

   }

 };

 static MarkActivationClosure mark_activation_closure;

 class SetHotnessClosure: public CodeBlobClosure {

 public:

   virtual void do_code_blob(CodeBlob* cb) {

     if (cb->is_nmethod()) {

       nmethod* nm = (nmethod*)cb;

       nm->set_hotness_counter(NMethodSweeper::hotness_counter_reset_val());

     }

   }

 };

 static SetHotnessClosure set_hotness_closure;

 int NMethodSweeper::hotness_counter_reset_val() {

   if (_hotness_counter_reset_val == 0) {

     _hotness_counter_reset_val = (ReservedCodeCacheSize < M) ? 1 : (ReservedCodeCacheSize / M) * 2;

   }

   return _hotness_counter_reset_val;

 }

 bool NMethodSweeper::sweep_in_progress() {

   return (_current != NULL);

 }

 // Scans the stacks of all Java threads and marks activations of not-entrant methods.

 // No need to synchronize access, since 'mark_active_nmethods' is always executed at a

 // safepoint.

 void NMethodSweeper::mark_active_nmethods() {

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

   // If we do not want to reclaim not-entrant or zombie methods there is no need

   // to scan stacks

   if (!MethodFlushing) {

     return;

   }

   // Increase time so that we can estimate when to invoke the sweeper again.

   _time_counter++;

   // Check for restart

   assert(CodeCache::find_blob_unsafe(_current) == _current, "Sweeper nmethod cached state invalid");

   if (!sweep_in_progress()) {

     _seen = 0;

     _sweep_fractions_left = NmethodSweepFraction;

     _current = CodeCache::first_nmethod();

     _traversals += 1;

     _total_time_this_sweep = Tickspan();

     if (PrintMethodFlushing) {

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

     }

     Threads::nmethods_do(&mark_activation_closure);

   } else {

     // Only set hotness counter

     Threads::nmethods_do(&set_hotness_closure);

   }

   OrderAccess::storestore();

 }

 /**

  * This function invokes the sweeper if at least one of the three conditions is met:

  *    (1) The code cache is getting full

  *    (2) There are sufficient state changes in/since the last sweep.

  *    (3) We have not been sweeping for 'some time'

  */

 void NMethodSweeper::possibly_sweep() {

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

   // Only compiler threads are allowed to sweep

   if (!MethodFlushing || !sweep_in_progress() || !Thread::current()->is_Compiler_thread()) {

     return;

   }

   // If there was no state change while nmethod sweeping, 'should_sweep' will be false.

   // This is one of the two places where should_sweep can be set to true. The general

   // idea is as follows: If there is enough free space in the code cache, there is no

   // need to invoke the sweeper. The following formula (which determines whether to invoke

   // the sweeper or not) depends on the assumption that for larger ReservedCodeCacheSizes

   // we need less frequent sweeps than for smaller ReservedCodecCacheSizes. Furthermore,

   // the formula considers how much space in the code cache is currently used. Here are

   // some examples that will (hopefully) help in understanding.

   //

   // Small ReservedCodeCacheSizes:  (e.g., < 16M) We invoke the sweeper every time, since

   //                                              the result of the division is 0. This

   //                                              keeps the used code cache size small

   //                                              (important for embedded Java)

   // Large ReservedCodeCacheSize :  (e.g., 256M + code cache is 10% full). The formula

   //                                              computes: (256 / 16) - 1 = 15

   //                                              As a result, we invoke the sweeper after

   //                                              15 invocations of 'mark_active_nmethods.

   // Large ReservedCodeCacheSize:   (e.g., 256M + code Cache is 90% full). The formula

   //                                              computes: (256 / 16) - 10 = 6.

   if (!_should_sweep) {

     int time_since_last_sweep = _time_counter - _last_sweep;

     double wait_until_next_sweep = (ReservedCodeCacheSize / (16 * M)) - time_since_last_sweep -

                                 CodeCache::reverse_free_ratio();

     if ((wait_until_next_sweep <= 0.0) || !CompileBroker::should_compile_new_jobs()) {

       _should_sweep = true;

     }

   }

   if (_should_sweep && _sweep_fractions_left > 0) {

     // Only one thread at a time will sweep

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

     if (old != 0) {

       return;

     }

 #ifdef ASSERT

     if (LogSweeper && _records == NULL) {

       // Create the ring buffer for the logging code

       _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);

       memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);

     }

 #endif

     if (_sweep_fractions_left > 0) {

       sweep_code_cache();

       _sweep_fractions_left--;

     }

     // We are done with sweeping the code cache once.

     if (_sweep_fractions_left == 0) {

       _last_sweep = _time_counter;

       // Reset flag; temporarily disables sweeper

       _should_sweep = false;

       // If there was enough state change, 'possibly_enable_sweeper()'

       // sets '_should_sweep' to true

       possibly_enable_sweeper();

       // Reset _bytes_changed only if there was enough state change. _bytes_changed

       // can further increase by calls to 'report_state_change'.

       if (_should_sweep) {

         _bytes_changed = 0;

       }

     }

     _sweep_started = 0;

   }

 }

 void NMethodSweeper::sweep_code_cache() {

   Ticks sweep_start_counter = Ticks::now();

   _flushed_count                = 0;

   _zombified_count              = 0;

   _marked_for_reclamation_count = 0;

   if (PrintMethodFlushing && Verbose) {

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

   }

   if (!CompileBroker::should_compile_new_jobs()) {

     // If we have turned off compilations we might as well do full sweeps

     // in order to reach the clean state faster. Otherwise the sleeping compiler

     // threads will slow down sweeping.

     _sweep_fractions_left = 1;

   }

   // 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) / _sweep_fractions_left;

   int swept_count = 0;

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

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

   int freed_memory = 0;

   {

     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 || _sweep_fractions_left == 1) && _current != NULL; i++) {

       swept_count++;

       if (SafepointSynchronize::is_synchronizing()) { // Safepoint request

         if (PrintMethodFlushing && Verbose) {

           tty->print_cr("### Sweep at %d out of %d, invocation: %d, yielding to safepoint", _seen, CodeCache::nof_nmethods(), _sweep_fractions_left);

         }

         MutexUnlockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);

         assert(Thread::current()->is_Java_thread(), "should be java thread");

         JavaThread* thread = (JavaThread*)Thread::current();

         ThreadBlockInVM tbivm(thread);

         thread->java_suspend_self();

       }

       // 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);

         freed_memory += process_nmethod(_current);

       }

       _seen++;

       _current = next;

     }

   }

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

   const Ticks sweep_end_counter = Ticks::now();

   const Tickspan sweep_time = sweep_end_counter - sweep_start_counter;

   _total_time_sweeping  += sweep_time;

   _total_time_this_sweep += sweep_time;

   _peak_sweep_fraction_time = MAX2(sweep_time, _peak_sweep_fraction_time);

   _total_nof_methods_reclaimed += _flushed_count;

   EventSweepCodeCache event(UNTIMED);

   if (event.should_commit()) {

     event.set_starttime(sweep_start_counter);

     event.set_endtime(sweep_end_counter);

     event.set_sweepIndex(_traversals);

     event.set_sweepFractionIndex(NmethodSweepFraction - _sweep_fractions_left + 1);

     event.set_sweptCount(swept_count);

     event.set_flushedCount(_flushed_count);

     event.set_markedCount(_marked_for_reclamation_count);

     event.set_zombifiedCount(_zombified_count);

     event.commit();

   }

 #ifdef ASSERT

   if(PrintMethodFlushing) {

     tty->print_cr("### sweeper:      sweep time(%d): "

       INT64_FORMAT, _sweep_fractions_left, (jlong)sweep_time.value());

   }

 #endif

   if (_sweep_fractions_left == 1) {

     _peak_sweep_time = MAX2(_peak_sweep_time, _total_time_this_sweep);

     log_sweep("finished");

   }

   // Sweeper is the only case where memory is released, check here if it

   // is time to restart the compiler. Only checking if there is a certain

   // amount of free memory in the code cache might lead to re-enabling

   // compilation although no memory has been released. For example, there are

   // cases when compilation was disabled although there is 4MB (or more) free

   // memory in the code cache. The reason is code cache fragmentation. Therefore,

   // it only makes sense to re-enable compilation if we have actually freed memory.

   // Note that typically several kB are released for sweeping 16MB of the code

   // cache. As a result, 'freed_memory' > 0 to restart the compiler.

   if (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0)) {

     CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);

     log_sweep("restart_compiler");

   }

 }

 /**

  * This function updates the sweeper statistics that keep track of nmethods

  * state changes. If there is 'enough' state change, the sweeper is invoked

  * as soon as possible. There can be data races on _bytes_changed. The data

  * races are benign, since it does not matter if we loose a couple of bytes.

  * In the worst case we call the sweeper a little later. Also, we are guaranteed

  * to invoke the sweeper if the code cache gets full.

  */

 void NMethodSweeper::report_state_change(nmethod* nm) {

   _bytes_changed += nm->total_size();

   possibly_enable_sweeper();

 }

 /**

  * Function determines if there was 'enough' state change in the code cache to invoke

  * the sweeper again. Currently, we determine 'enough' as more than 1% state change in

  * the code cache since the last sweep.

  */

 void NMethodSweeper::possibly_enable_sweeper() {

   double percent_changed = ((double)_bytes_changed / (double)ReservedCodeCacheSize) * 100;

   if (percent_changed > 1.0) {

     _should_sweep = true;

   }

 }

 class NMethodMarker: public StackObj {

  private:

   CompilerThread* _thread;

  public:

   NMethodMarker(nmethod* nm) {

     _thread = CompilerThread::current();

     if (!nm->is_zombie() && !nm->is_unloaded()) {

       // Only expose live nmethods for scanning

       _thread->set_scanned_nmethod(nm);

     }

   }

   ~NMethodMarker() {

     _thread->set_scanned_nmethod(NULL);

   }

 };

 void NMethodSweeper::release_nmethod(nmethod *nm) {

   // Clean up any CompiledICHolders

   {

     ResourceMark rm;

     MutexLocker ml_patch(CompiledIC_lock);

     RelocIterator iter(nm);

     while (iter.next()) {

       if (iter.type() == relocInfo::virtual_call_type) {

         CompiledIC::cleanup_call_site(iter.virtual_call_reloc());

       }

     }

   }

   MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);

   nm->flush();

 }

 int NMethodSweeper::process_nmethod(nmethod *nm) {

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

   int freed_memory = 0;

   // Make sure this nmethod doesn't get unloaded during the scan,

   // since safepoints may happen during acquired below locks.

   NMethodMarker nmm(nm);

   SWEEP(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 inline caches that point to zombie/non-entrant methods

       MutexLocker cl(CompiledIC_lock);

       nm->cleanup_inline_caches();

       SWEEP(nm);

     }

     return freed_memory;

   }

   if (nm->is_zombie()) {

     // If it is the first time we see nmethod then we mark it. Otherwise,

     // we reclaim 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);

       }

       freed_memory = nm->total_size();

       release_nmethod(nm);

       _flushed_count++;

     } else {

       if (PrintMethodFlushing && Verbose) {

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

       }

       nm->mark_for_reclamation();

       // Keep track of code cache state change

       _bytes_changed += nm->total_size();

       _marked_for_reclamation_count++;

       SWEEP(nm);

     }

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

     // If there are 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);

       }

       // Code cache state change is tracked in make_zombie()

       nm->make_zombie();

       _zombified_count++;

       SWEEP(nm);

     } else {

       // Still alive, clean up its inline caches

       MutexLocker cl(CompiledIC_lock);

       nm->cleanup_inline_caches();

       SWEEP(nm);

     }

   } 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()) {

       SWEEP(nm);

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

       freed_memory = nm->total_size();

       release_nmethod(nm);

       _flushed_count++;

     } else {

       // Code cache state change is tracked in make_zombie()

       nm->make_zombie();

       _zombified_count++;

       SWEEP(nm);

     }

   } else {

     if (UseCodeCacheFlushing) {

       if (!nm->is_locked_by_vm() && !nm->is_osr_method() && !nm->is_native_method()) {

         // Do not make native methods and OSR-methods not-entrant

         nm->dec_hotness_counter();

         // Get the initial value of the hotness counter. This value depends on the

         // ReservedCodeCacheSize

         int reset_val = hotness_counter_reset_val();

         int time_since_reset = reset_val - nm->hotness_counter();

         double threshold = -reset_val + (CodeCache::reverse_free_ratio() * NmethodSweepActivity);

         // The less free space in the code cache we have - the bigger reverse_free_ratio() is.

         // I.e., 'threshold' increases with lower available space in the code cache and a higher

         // NmethodSweepActivity. If the current hotness counter - which decreases from its initial

         // value until it is reset by stack walking - is smaller than the computed threshold, the

         // corresponding nmethod is considered for removal.

         if ((NmethodSweepActivity > 0) && (nm->hotness_counter() < threshold) && (time_since_reset > 10)) {

           // A method is marked as not-entrant if the method is

           // 1) 'old enough': nm->hotness_counter() < threshold

           // 2) The method was in_use for a minimum amount of time: (time_since_reset > 10)

           //    The second condition is necessary if we are dealing with very small code cache

           //    sizes (e.g., <10m) and the code cache size is too small to hold all hot methods.

           //    The second condition ensures that methods are not immediately made not-entrant

           //    after compilation.

           nm->make_not_entrant();

           // Code cache state change is tracked in make_not_entrant()

           if (PrintMethodFlushing && Verbose) {

             tty->print_cr("### Nmethod %d/" PTR_FORMAT "made not-entrant: hotness counter %d/%d threshold %f",

                           nm->compile_id(), nm, nm->hotness_counter(), reset_val, threshold);

           }

         }

       }

     }

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

     MutexLocker cl(CompiledIC_lock);

     nm->cleanup_inline_caches();

     SWEEP(nm);

   }

   return freed_memory;

 }

 // 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) {

     stringStream s;

     // Dump code cache state into a buffer before locking the tty,

     // because log_state() will use locks causing lock conflicts.

     CodeCache::log_state(&s);

     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(s.as_string());

   }

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

     stringStream s;

     // Dump code cache state into a buffer before locking the tty,

     // because log_state() will use locks causing lock conflicts.

     CodeCache::log_state(&s);

     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(s.as_string());

     xtty->stamp();

     xtty->end_elem();

   }

 }