src/share/vm/runtime/sweeper.cpp
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@@ -125,68 +125,88 @@
}
#else
#define SWEEP(nm)
#endif
-
-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
+long NMethodSweeper::_traversals = 0; // Nof. stack traversals performed
+int NMethodSweeper::_seen = 0; // Nof. nmethods 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_count = 0; // Nof. nmethods marked for reclaim in current sweep
-volatile int NMethodSweeper::_invocations = 0; // No. of invocations left until we are completed with this pass
+volatile int NMethodSweeper::_invocations = 0; // Nof. 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::_resweep = false;
-jint NMethodSweeper::_flush_token = 0;
-jlong NMethodSweeper::_last_full_flush_time = 0;
-int NMethodSweeper::_highest_marked = 0;
-int NMethodSweeper::_dead_compile_ids = 0;
-long NMethodSweeper::_last_flush_traversal_id = 0;
+bool NMethodSweeper::_request_mark_phase = false;
-int NMethodSweeper::_number_of_flushes = 0; // Total of full traversals caused by full cache
int NMethodSweeper::_total_nof_methods_reclaimed = 0;
jlong NMethodSweeper::_total_time_sweeping = 0;
jlong NMethodSweeper::_total_time_this_sweep = 0;
jlong NMethodSweeper::_peak_sweep_time = 0;
jlong NMethodSweeper::_peak_sweep_fraction_time = 0;
-jlong NMethodSweeper::_total_disconnect_time = 0;
-jlong NMethodSweeper::_peak_disconnect_time = 0;
+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 (cb->is_nmethod() && ((nmethod*)cb)->is_not_entrant()) {
- ((nmethod*)cb)->mark_as_seen_on_stack();
+ 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);
}
-void NMethodSweeper::scan_stacks() {
+// 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 (!MethodFlushing) return;
-
- // No need to synchronize access, since this is always 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;
+ }
// 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 (!sweep_in_progress() && _resweep) {
+ if (!sweep_in_progress() && need_marking_phase()) {
_seen = 0;
_invocations = NmethodSweepFraction;
_current = CodeCache::first_nmethod();
_traversals += 1;
_total_time_this_sweep = 0;
@@ -195,34 +215,24 @@
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.
- _resweep = false;
+ reset_nmethod_marking();
_locked_seen = 0;
_not_entrant_seen_on_stack = 0;
- }
-
- if (UseCodeCacheFlushing) {
- // only allow new flushes after the interval is complete.
- jlong now = os::javaTimeMillis();
- jlong max_interval = (jlong)MinCodeCacheFlushingInterval * (jlong)1000;
- jlong curr_interval = now - _last_full_flush_time;
- if (curr_interval > max_interval) {
- _flush_token = 0;
- }
-
- if (!CodeCache::needs_flushing() && !CompileBroker::should_compile_new_jobs()) {
- CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
- log_sweep("restart_compiler");
- }
+ // Only set hotness counter
+ } else {
+ Threads::nmethods_do(&set_hotness_closure);
}
}
void NMethodSweeper::possibly_sweep() {
assert(JavaThread::current()->thread_state() == _thread_in_vm, "must run in vm mode");
- if (!MethodFlushing || !sweep_in_progress()) return;
+ if (!MethodFlushing || !sweep_in_progress()) {
+ return;
+ }
if (_invocations > 0) {
// Only one thread at a time will sweep
jint old = Atomic::cmpxchg( 1, &_sweep_started, 0 );
if (old != 0) {
@@ -256,25 +266,23 @@
}
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. After a few iterations the cache
- // will be clean and sweeping stops (_resweep will not be set)
+ // threads will slow down sweeping.
_invocations = 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;
-
assert(!SafepointSynchronize::is_at_safepoint(), "should not be in safepoint when we get here");
assert(!CodeCache_lock->owned_by_self(), "just checking");
-
+ int flushed_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++) {
@@ -295,23 +303,23 @@
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);
+ flushed_memory += process_nmethod(_current);
}
_seen++;
_current = next;
}
}
assert(_invocations > 1 || _current == NULL, "must have scanned the whole cache");
- if (!sweep_in_progress() && !_resweep && (_locked_seen || _not_entrant_seen_on_stack)) {
+ 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 aggresively
+ // 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");
@@ -347,13 +355,19 @@
if (_invocations == 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.
- if (UseCodeCacheFlushing && !CompileBroker::should_compile_new_jobs() && !CodeCache::needs_flushing()) {
+ // 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 per sweep cycle (16MB).
+ if (UseCodeCacheFlushing && (!CompileBroker::should_compile_new_jobs() && (flushed_memory > 0))) {
CompileBroker::set_should_compile_new_jobs(CompileBroker::run_compilation);
log_sweep("restart_compiler");
}
}
@@ -388,63 +402,64 @@
MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
nm->flush();
}
-void NMethodSweeper::process_nmethod(nmethod *nm) {
+int NMethodSweeper::process_nmethod(nmethod *nm) {
assert(!CodeCache_lock->owned_by_self(), "just checking");
+ int flushed_memory = 0;
// Make sure this nmethod doesn't get unloaded during the scan,
- // since the locks acquired below might safepoint.
+ // since the locks acquired might below the safepoint.
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-up all inline caches that points to zombie/non-reentrant methods
+ // 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;
+ return flushed_memory;
}
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
+ // 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);
}
+ flushed_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();
- _resweep = true;
+ request_nmethod_marking();
_marked_count++;
SWEEP(nm);
}
} else if (nm->is_not_entrant()) {
- // If there is no current activations of this method on the
+ // 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);
}
nm->make_zombie();
- _resweep = true;
+ request_nmethod_marking();
_zombified_count++;
SWEEP(nm);
} else {
// Still alive, clean up its inline caches
MutexLocker cl(CompiledIC_lock);
@@ -455,163 +470,55 @@
_not_entrant_seen_on_stack++;
SWEEP(nm);
}
} else if (nm->is_unloaded()) {
// Unloaded code, just make it a zombie
- if (PrintMethodFlushing && Verbose)
+ 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
+ flushed_memory = nm->total_size();
release_nmethod(nm);
_flushed_count++;
} else {
nm->make_zombie();
- _resweep = true;
+ request_nmethod_marking();
_zombified_count++;
SWEEP(nm);
}
} else {
- assert(nm->is_alive(), "should be alive");
-
if (UseCodeCacheFlushing) {
- if (nm->is_speculatively_disconnected() && !nm->is_locked_by_vm() && !nm->is_osr_method() &&
- (_traversals > _last_flush_traversal_id + 2) && (nm->compile_id() < _highest_marked)) {
- // This method has not been called since the forced cleanup happened
+ 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();
+ // This method is cold and the code cache fills up => get rid of it.
+ 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);
+ // A method is marked as not-entrance 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
+ // just after compilation.
+ if ((nm->hotness_counter() < threshold) && (time_since_reset > 10)) {
nm->make_not_entrant();
+ request_nmethod_marking();
}
}
-
- // Clean-up all inline caches that points to zombie/non-reentrant methods
+ }
+ // Clean-up all inline caches that point to zombie/non-reentrant methods
MutexLocker cl(CompiledIC_lock);
nm->cleanup_inline_caches();
SWEEP(nm);
}
+ return flushed_memory;
}
-// 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 Method*'s
-// _code field is restored and the Method*/nmethod
-// go back to their normal state.
-void NMethodSweeper::handle_full_code_cache(bool is_full) {
-
- if (is_full) {
- // Since code cache is full, immediately stop new compiles
- if (CompileBroker::set_should_compile_new_jobs(CompileBroker::stop_compilation)) {
- log_sweep("disable_compiler");
- }
- }
-
- // Make sure only one thread can flush
- // The token is reset after CodeCacheMinimumFlushInterval in scan stacks,
- // no need to check the timeout here.
- jint old = Atomic::cmpxchg( 1, &_flush_token, 0 );
- if (old != 0) {
- return;
- }
-
- VM_HandleFullCodeCache op(is_full);
- VMThread::execute(&op);
-
- // resweep again as soon as possible
- _resweep = 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
-
- jlong disconnect_start_counter = os::elapsed_counter();
-
- // Traverse the code cache trying to dump the oldest nmethods
- int curr_max_comp_id = CompileBroker::get_compilation_id();
- int flush_target = ((curr_max_comp_id - _dead_compile_ids) / CodeCacheFlushingFraction) + _dead_compile_ids;
-
- log_sweep("start_cleaning");
-
- nmethod* nm = CodeCache::alive_nmethod(CodeCache::first());
- jint disconnected = 0;
- jint made_not_entrant = 0;
- jint nmethod_count = 0;
-
- while ((nm != NULL)){
- int 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_osr_method() && !nm->is_locked_by_vm() && !nm->is_native_method()) {
-
- // only count methods that can be speculatively disconnected
- nmethod_count++;
-
- if (nm->is_in_use() && (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
- CompilationPolicy::policy()->delay_compilation(nm->method());
- 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));
- }
-
- // remember how many compile_ids wheren't seen last flush.
- _dead_compile_ids = curr_max_comp_id - nmethod_count;
-
- 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 (is_full) {
- _last_full_flush_time = os::javaTimeMillis();
- }
-
- jlong disconnect_end_counter = os::elapsed_counter();
- jlong disconnect_time = disconnect_end_counter - disconnect_start_counter;
- _total_disconnect_time += disconnect_time;
- _peak_disconnect_time = MAX2(disconnect_time, _peak_disconnect_time);
-
- EventCleanCodeCache event(UNTIMED);
- if (event.should_commit()) {
- event.set_starttime(disconnect_start_counter);
- event.set_endtime(disconnect_end_counter);
- event.set_disconnectedCount(disconnected);
- event.set_madeNonEntrantCount(made_not_entrant);
- event.commit();
- }
- _number_of_flushes++;
-
- // After two more traversals the sweeper will get rid of unrestored nmethods
- _last_flush_traversal_id = _traversals;
- _resweep = true;
-#ifdef ASSERT
-
- if(PrintMethodFlushing && Verbose) {
- tty->print_cr("### sweeper: unload time: " INT64_FORMAT, (jlong)disconnect_time);
- }
-#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) {
stringStream s;