jdk-sandbox: comparison hotspot/src/share/vm/runtime/sweeper.cpp

equal deleted inserted replaced

-:d47713227456
+:6a9645992cee
 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 = _invocations;
+_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
+nmethod* NMethodSweeper::_current                      = NULL; // Current nmethod
-long      NMethodSweeper::_traversals      = 0;    // Nof. stack traversals performed
+long     NMethodSweeper::_traversals                   = 0;    // Stack scan count, also sweep ID.
-int       NMethodSweeper::_seen            = 0;    // Nof. nmethods we have currently processed in current pass of CodeCache
+long     NMethodSweeper::_time_counter                 = 0;    // Virtual time used to periodically invoke sweeper
-int       NMethodSweeper::_flushed_count   = 0;    // Nof. nmethods flushed in current sweep
+long     NMethodSweeper::_last_sweep                   = 0;    // Value of _time_counter when the last sweep happened
-int       NMethodSweeper::_zombified_count = 0;    // Nof. nmethods made zombie in current sweep
+int      NMethodSweeper::_seen                         = 0;    // Nof. nmethod we have currently processed in current pass of CodeCache
-int       NMethodSweeper::_marked_count    = 0;    // Nof. nmethods marked for reclaim in current sweep
+int      NMethodSweeper::_flushed_count                = 0;    // Nof. nmethods flushed in current sweep
+int      NMethodSweeper::_zombified_count              = 0;    // Nof. nmethods made zombie in current sweep
-volatile int NMethodSweeper::_invocations   = 0; // Nof. invocations left until we are completed with this pass
+int      NMethodSweeper::_marked_for_reclamation_count = 0;    // Nof. nmethods marked for reclaim in current sweep
-volatile int NMethodSweeper::_sweep_started = 0; // Whether a sweep is in progress.
+volatile bool NMethodSweeper::_should_sweep            = true; // Indicates if we should invoke the sweeper
-jint      NMethodSweeper::_locked_seen               = 0;
+volatile int  NMethodSweeper::_sweep_fractions_left    = 0;    // Nof. invocations left until we are completed with this pass
-jint      NMethodSweeper::_not_entrant_seen_on_stack = 0;
+volatile int  NMethodSweeper::_sweep_started           = 0;    // Flag to control conc sweeper
-bool      NMethodSweeper::_request_mark_phase        = false;
+volatile int  NMethodSweeper::_bytes_changed           = 0;    // Counts the total nmethod size if the nmethod changed from:
+//   1) alive       -> not_entrant
-int       NMethodSweeper::_total_nof_methods_reclaimed = 0;
+//   2) not_entrant -> zombie
-jlong     NMethodSweeper::_total_time_sweeping         = 0;
+//   3) zombie      -> marked_for_reclamation
-jlong     NMethodSweeper::_total_time_this_sweep       = 0;
-jlong     NMethodSweeper::_peak_sweep_time             = 0;
+int   NMethodSweeper::_total_nof_methods_reclaimed     = 0;    // Accumulated nof methods flushed
-jlong     NMethodSweeper::_peak_sweep_fraction_time    = 0;
+jlong NMethodSweeper::_total_time_sweeping             = 0;    // Accumulated time sweeping
-int       NMethodSweeper::_hotness_counter_reset_val   = 0;
+jlong NMethodSweeper::_total_time_this_sweep           = 0;    // Total time this sweep
+jlong NMethodSweeper::_peak_sweep_time                 = 0;    // Peak time for a full sweep
+jlong NMethodSweeper::_peak_sweep_fraction_time        = 0;    // Peak time sweeping one fraction
+int   NMethodSweeper::_hotness_counter_reset_val       = 0;
 class MarkActivationClosure: public CodeBlobClosure {
 public:
 virtual void do_code_blob(CodeBlob* cb) {
 // 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() && need_marking_phase()) {
+if (!sweep_in_progress()) {
-_seen        = 0;
+_seen = 0;
-_invocations = NmethodSweepFraction;
+_sweep_fractions_left = NmethodSweepFraction;
-_current     = CodeCache::first_nmethod();
+_current = CodeCache::first_nmethod();
-_traversals  += 1;
+_traversals += 1;
 _total_time_this_sweep = 0;
 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.
-reset_nmethod_marking();
-_locked_seen = 0;
-_not_entrant_seen_on_stack = 0;
 } 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");
 if (!MethodFlushing || !sweep_in_progress()) {
 return;
 }
-if (_invocations > 0) {
+// 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;
 }
 // Create the ring buffer for the logging code
 _records = NEW_C_HEAP_ARRAY(SweeperRecord, SweeperLogEntries, mtGC);
 memset(_records, 0, sizeof(SweeperRecord) * SweeperLogEntries);
 }
 #endif
-if (_invocations > 0) {
+if (_sweep_fractions_left > 0) {
 sweep_code_cache();
-_invocations--;
+_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() {
 jlong sweep_start_counter = os::elapsed_counter();
-_flushed_count   = 0;
+_flushed_count                = 0;
-_zombified_count = 0;
+_zombified_count              = 0;
-_marked_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(), _invocations);
+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.
-_invocations = 1;
+_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) / _invocations;
+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 || _invocations == 1) && _current != NULL; i++) {
+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(), _invocations);
+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();
 _seen++;
 _current = next;
 }
 }
-assert(_invocations > 1 || _current == NULL, "must have scanned the whole cache");
+assert(_sweep_fractions_left > 1 || _current == NULL, "must have scanned the whole cache");
-if (!sweep_in_progress() && !need_marking_phase() && (_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 aggressively
-// 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");
-}
-}
 jlong sweep_end_counter = os::elapsed_counter();
 jlong sweep_time = sweep_end_counter - sweep_start_counter;
 _total_time_sweeping  += sweep_time;
 _total_time_this_sweep += sweep_time;
 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 - _invocations + 1);
+event.set_sweepFractionIndex(NmethodSweepFraction - _sweep_fractions_left + 1);
 event.set_sweptCount(swept_count);
 event.set_flushedCount(_flushed_count);
-event.set_markedCount(_marked_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, _invocations, (jlong)sweep_time);
+tty->print_cr("### sweeper:      sweep time(%d): " INT64_FORMAT, _sweep_fractions_left, (jlong)sweep_time);
 }
 #endif
-if (_invocations == 1) {
+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
 // 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 (UseCodeCacheFlushing && (!CompileBroker::should_compile_new_jobs() && (freed_memory > 0))) {
+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:
 if (nm->is_alive()) {
 // Clean inline caches that point to zombie/non-entrant methods
 MutexLocker cl(CompiledIC_lock);
 nm->cleanup_inline_caches();
 SWEEP(nm);
-} else {
-_locked_seen++;
-SWEEP(nm);
 }
 return freed_memory;
 }
 if (nm->is_zombie()) {
 } else {
 if (PrintMethodFlushing && Verbose) {
 tty->print_cr("### Nmethod %3d/" PTR_FORMAT " (zombie) being marked for reclamation", nm->compile_id(), nm);
 }
 nm->mark_for_reclamation();
-request_nmethod_marking();
+// Keep track of code cache state change
-_marked_count++;
+_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();
-request_nmethod_marking();
 _zombified_count++;
 SWEEP(nm);
 } 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++;
 SWEEP(nm);
 }
 } else if (nm->is_unloaded()) {
 // Unloaded code, just make it a zombie
 if (PrintMethodFlushing && Verbose) {
 // 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();
-request_nmethod_marking();
 _zombified_count++;
 SWEEP(nm);
 }
 } else {
 if (UseCodeCacheFlushing) {
 //    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();
-request_nmethod_marking();
+// 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);

changeset 21575	6a9645992cee
parent 20290	2127dc70bce9
child 21727	4a5fc611c9a7