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8325574: Shenandoah: Simplify and enhance reporting of requested GCs
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Reviewed-by: ysr, kdnilsen, shade
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William Kemper committed Feb 14, 2024
1 parent 09d4936 commit b823fa4
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Showing 5 changed files with 108 additions and 104 deletions.
110 changes: 80 additions & 30 deletions src/hotspot/share/gc/shenandoah/shenandoahCollectorPolicy.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -38,31 +38,17 @@ ShenandoahCollectorPolicy::ShenandoahCollectorPolicy() :
_consecutive_degenerated_gcs(0),
_alloc_failure_degenerated(0),
_alloc_failure_degenerated_upgrade_to_full(0),
_alloc_failure_full(0),
_explicit_concurrent(0),
_explicit_full(0),
_implicit_concurrent(0),
_implicit_full(0) {
_alloc_failure_full(0) {

Copy::zero_to_bytes(_degen_points, sizeof(size_t) * ShenandoahGC::_DEGENERATED_LIMIT);
Copy::zero_to_bytes(_degen_point_counts, sizeof(size_t) * ShenandoahGC::_DEGENERATED_LIMIT);
Copy::zero_to_bytes(_collection_cause_counts, sizeof(size_t) * GCCause::_last_gc_cause);

_tracer = new ShenandoahTracer();
}

void ShenandoahCollectorPolicy::record_explicit_to_concurrent() {
_explicit_concurrent++;
}

void ShenandoahCollectorPolicy::record_explicit_to_full() {
_explicit_full++;
}

void ShenandoahCollectorPolicy::record_implicit_to_concurrent() {
_implicit_concurrent++;
}

void ShenandoahCollectorPolicy::record_implicit_to_full() {
_implicit_full++;
void ShenandoahCollectorPolicy::record_collection_cause(GCCause::Cause cause) {
assert(cause < GCCause::_last_gc_cause, "Invalid GCCause");
_collection_cause_counts[cause]++;
}

void ShenandoahCollectorPolicy::record_alloc_failure_to_full() {
Expand All @@ -72,7 +58,7 @@ void ShenandoahCollectorPolicy::record_alloc_failure_to_full() {
void ShenandoahCollectorPolicy::record_alloc_failure_to_degenerated(ShenandoahGC::ShenandoahDegenPoint point) {
assert(point < ShenandoahGC::_DEGENERATED_LIMIT, "sanity");
_alloc_failure_degenerated++;
_degen_points[point]++;
_degen_point_counts[point]++;
}

void ShenandoahCollectorPolicy::record_degenerated_upgrade_to_full() {
Expand Down Expand Up @@ -109,6 +95,44 @@ bool ShenandoahCollectorPolicy::is_at_shutdown() {
return _in_shutdown.is_set();
}

bool is_explicit_gc(GCCause::Cause cause) {
return GCCause::is_user_requested_gc(cause)
|| GCCause::is_serviceability_requested_gc(cause);
}

bool is_implicit_gc(GCCause::Cause cause) {
return cause != GCCause::_allocation_failure
&& cause != GCCause::_shenandoah_concurrent_gc
&& !is_explicit_gc(cause);
}

#ifdef ASSERT
bool is_valid_request(GCCause::Cause cause) {
return is_explicit_gc(cause)
|| cause == GCCause::_metadata_GC_clear_soft_refs
|| cause == GCCause::_codecache_GC_aggressive
|| cause == GCCause::_codecache_GC_threshold
|| cause == GCCause::_full_gc_alot
|| cause == GCCause::_wb_young_gc
|| cause == GCCause::_wb_full_gc
|| cause == GCCause::_wb_breakpoint
|| cause == GCCause::_scavenge_alot;
}
#endif

bool ShenandoahCollectorPolicy::should_run_full_gc(GCCause::Cause cause) {
return is_explicit_gc(cause) ? !ExplicitGCInvokesConcurrent : !ShenandoahImplicitGCInvokesConcurrent;
}

bool ShenandoahCollectorPolicy::should_handle_requested_gc(GCCause::Cause cause) {
assert(is_valid_request(cause), "only requested GCs here: %s", GCCause::to_string(cause));

if (DisableExplicitGC) {
return !is_explicit_gc(cause);
}
return true;
}

void ShenandoahCollectorPolicy::print_gc_stats(outputStream* out) const {
out->print_cr("Under allocation pressure, concurrent cycles may cancel, and either continue cycle");
out->print_cr("under stop-the-world pause or result in stop-the-world Full GC. Increase heap size,");
Expand All @@ -119,10 +143,32 @@ void ShenandoahCollectorPolicy::print_gc_stats(outputStream* out) const {

size_t completed_gcs = _success_full_gcs + _success_degenerated_gcs + _success_concurrent_gcs;
out->print_cr(SIZE_FORMAT_W(5) " Completed GCs", completed_gcs);
out->print_cr(SIZE_FORMAT_W(5) " Successful Concurrent GCs (%.2f%%)", _success_concurrent_gcs, percent_of(_success_concurrent_gcs, completed_gcs));
out->print_cr(" " SIZE_FORMAT_W(5) " invoked explicitly (%.2f%%)", _explicit_concurrent, percent_of(_explicit_concurrent, _success_concurrent_gcs));
out->print_cr(" " SIZE_FORMAT_W(5) " invoked implicitly (%.2f%%)", _implicit_concurrent, percent_of(_implicit_concurrent, _success_concurrent_gcs));
out->print_cr(" " SIZE_FORMAT_W(5) " abbreviated (%.2f%%)", _abbreviated_concurrent_gcs, percent_of(_abbreviated_concurrent_gcs, _success_concurrent_gcs));

size_t explicit_requests = 0;
size_t implicit_requests = 0;
for (int c = 0; c < GCCause::_last_gc_cause; c++) {
size_t cause_count = _collection_cause_counts[c];
if (cause_count > 0) {
auto cause = (GCCause::Cause) c;
if (is_explicit_gc(cause)) {
explicit_requests += cause_count;
} else if (is_implicit_gc(cause)) {
implicit_requests += cause_count;
}
const char* desc = GCCause::to_string(cause);
out->print_cr(" " SIZE_FORMAT_W(5) " caused by %s (%.2f%%)", cause_count, desc, percent_of(cause_count, completed_gcs));
}
}

out->cr();
out->print_cr(SIZE_FORMAT_W(5) " Successful Concurrent GCs (%.2f%%)", _success_concurrent_gcs, percent_of(_success_concurrent_gcs, completed_gcs));
if (ExplicitGCInvokesConcurrent) {
out->print_cr(" " SIZE_FORMAT_W(5) " invoked explicitly (%.2f%%)", explicit_requests, percent_of(explicit_requests, _success_concurrent_gcs));
}
if (ShenandoahImplicitGCInvokesConcurrent) {
out->print_cr(" " SIZE_FORMAT_W(5) " invoked implicitly (%.2f%%)", implicit_requests, percent_of(implicit_requests, _success_concurrent_gcs));
}
out->print_cr(" " SIZE_FORMAT_W(5) " abbreviated (%.2f%%)", _abbreviated_concurrent_gcs, percent_of(_abbreviated_concurrent_gcs, _success_concurrent_gcs));
out->cr();

size_t degenerated_gcs = _alloc_failure_degenerated_upgrade_to_full + _success_degenerated_gcs;
Expand All @@ -131,16 +177,20 @@ void ShenandoahCollectorPolicy::print_gc_stats(outputStream* out) const {
out->print_cr(" " SIZE_FORMAT_W(5) " caused by allocation failure (%.2f%%)", _alloc_failure_degenerated, percent_of(_alloc_failure_degenerated, degenerated_gcs));
out->print_cr(" " SIZE_FORMAT_W(5) " abbreviated (%.2f%%)", _abbreviated_degenerated_gcs, percent_of(_abbreviated_degenerated_gcs, degenerated_gcs));
for (int c = 0; c < ShenandoahGC::_DEGENERATED_LIMIT; c++) {
if (_degen_points[c] > 0) {
if (_degen_point_counts[c] > 0) {
const char* desc = ShenandoahGC::degen_point_to_string((ShenandoahGC::ShenandoahDegenPoint)c);
out->print_cr(" " SIZE_FORMAT_W(5) " happened at %s", _degen_points[c], desc);
out->print_cr(" " SIZE_FORMAT_W(5) " happened at %s", _degen_point_counts[c], desc);
}
}
out->cr();

out->print_cr(SIZE_FORMAT_W(5) " Full GCs (%.2f%%)", _success_full_gcs, percent_of(_success_full_gcs, completed_gcs));
out->print_cr(" " SIZE_FORMAT_W(5) " invoked explicitly (%.2f%%)", _explicit_full, percent_of(_explicit_full, _success_full_gcs));
out->print_cr(" " SIZE_FORMAT_W(5) " invoked implicitly (%.2f%%)", _implicit_full, percent_of(_implicit_full, _success_full_gcs));
out->print_cr(SIZE_FORMAT_W(5) " Full GCs (%.2f%%)", _success_full_gcs, percent_of(_success_full_gcs, completed_gcs));
if (!ExplicitGCInvokesConcurrent) {
out->print_cr(" " SIZE_FORMAT_W(5) " invoked explicitly (%.2f%%)", explicit_requests, percent_of(explicit_requests, _success_concurrent_gcs));
}
if (!ShenandoahImplicitGCInvokesConcurrent) {
out->print_cr(" " SIZE_FORMAT_W(5) " invoked implicitly (%.2f%%)", implicit_requests, percent_of(implicit_requests, _success_concurrent_gcs));
}
out->print_cr(" " SIZE_FORMAT_W(5) " caused by allocation failure (%.2f%%)", _alloc_failure_full, percent_of(_alloc_failure_full, _success_full_gcs));
out->print_cr(" " SIZE_FORMAT_W(5) " upgraded from Degenerated GC (%.2f%%)", _alloc_failure_degenerated_upgrade_to_full, percent_of(_alloc_failure_degenerated_upgrade_to_full, _success_full_gcs));
}
15 changes: 6 additions & 9 deletions src/hotspot/share/gc/shenandoah/shenandoahCollectorPolicy.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -48,11 +48,8 @@ class ShenandoahCollectorPolicy : public CHeapObj<mtGC> {
size_t _alloc_failure_degenerated;
size_t _alloc_failure_degenerated_upgrade_to_full;
size_t _alloc_failure_full;
size_t _explicit_concurrent;
size_t _explicit_full;
size_t _implicit_concurrent;
size_t _implicit_full;
size_t _degen_points[ShenandoahGC::_DEGENERATED_LIMIT];
size_t _collection_cause_counts[GCCause::_last_gc_cause];
size_t _degen_point_counts[ShenandoahGC::_DEGENERATED_LIMIT];

ShenandoahSharedFlag _in_shutdown;
ShenandoahTracer* _tracer;
Expand All @@ -72,10 +69,7 @@ class ShenandoahCollectorPolicy : public CHeapObj<mtGC> {
void record_alloc_failure_to_degenerated(ShenandoahGC::ShenandoahDegenPoint point);
void record_alloc_failure_to_full();
void record_degenerated_upgrade_to_full();
void record_explicit_to_concurrent();
void record_explicit_to_full();
void record_implicit_to_concurrent();
void record_implicit_to_full();
void record_collection_cause(GCCause::Cause cause);

void record_shutdown();
bool is_at_shutdown();
Expand All @@ -94,6 +88,9 @@ class ShenandoahCollectorPolicy : public CHeapObj<mtGC> {
inline size_t consecutive_degenerated_gc_count() const {
return _consecutive_degenerated_gcs;
}

static bool should_run_full_gc(GCCause::Cause cause);
static bool should_handle_requested_gc(GCCause::Cause cause);
};

#endif // SHARE_GC_SHENANDOAH_SHENANDOAHCOLLECTORPOLICY_HPP
84 changes: 21 additions & 63 deletions src/hotspot/share/gc/shenandoah/shenandoahControlThread.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -55,8 +55,8 @@ ShenandoahControlThread::ShenandoahControlThread() :
void ShenandoahControlThread::run_service() {
ShenandoahHeap* heap = ShenandoahHeap::heap();

GCMode default_mode = concurrent_normal;
GCCause::Cause default_cause = GCCause::_shenandoah_concurrent_gc;
const GCMode default_mode = concurrent_normal;
const GCCause::Cause default_cause = GCCause::_shenandoah_concurrent_gc;
int sleep = ShenandoahControlIntervalMin;

double last_shrink_time = os::elapsedTime();
Expand All @@ -66,23 +66,21 @@ void ShenandoahControlThread::run_service() {
// Having a period 10x lower than the delay would mean we hit the
// shrinking with lag of less than 1/10-th of true delay.
// ShenandoahUncommitDelay is in msecs, but shrink_period is in seconds.
double shrink_period = (double)ShenandoahUncommitDelay / 1000 / 10;
const double shrink_period = (double)ShenandoahUncommitDelay / 1000 / 10;

ShenandoahCollectorPolicy* policy = heap->shenandoah_policy();
ShenandoahHeuristics* heuristics = heap->heuristics();
ShenandoahCollectorPolicy* const policy = heap->shenandoah_policy();
ShenandoahHeuristics* const heuristics = heap->heuristics();
while (!in_graceful_shutdown() && !should_terminate()) {
// Figure out if we have pending requests.
bool alloc_failure_pending = _alloc_failure_gc.is_set();
bool is_gc_requested = _gc_requested.is_set();
GCCause::Cause requested_gc_cause = _requested_gc_cause;
bool explicit_gc_requested = is_gc_requested && is_explicit_gc(requested_gc_cause);
bool implicit_gc_requested = is_gc_requested && !is_explicit_gc(requested_gc_cause);
const bool alloc_failure_pending = _alloc_failure_gc.is_set();
const bool is_gc_requested = _gc_requested.is_set();
const GCCause::Cause requested_gc_cause = _requested_gc_cause;

// This control loop iteration has seen this much allocation.
size_t allocs_seen = Atomic::xchg(&_allocs_seen, (size_t)0, memory_order_relaxed);
const size_t allocs_seen = Atomic::xchg(&_allocs_seen, (size_t)0, memory_order_relaxed);

// Check if we have seen a new target for soft max heap size.
bool soft_max_changed = heap->check_soft_max_changed();
const bool soft_max_changed = heap->check_soft_max_changed();

// Choose which GC mode to run in. The block below should select a single mode.
GCMode mode = none;
Expand All @@ -109,36 +107,17 @@ void ShenandoahControlThread::run_service() {
mode = stw_full;
}

} else if (explicit_gc_requested) {
} else if (is_gc_requested) {
cause = requested_gc_cause;
log_info(gc)("Trigger: Explicit GC request (%s)", GCCause::to_string(cause));

log_info(gc)("Trigger: GC request (%s)", GCCause::to_string(cause));
heuristics->record_requested_gc();

if (ExplicitGCInvokesConcurrent) {
policy->record_explicit_to_concurrent();
mode = default_mode;
// Unload and clean up everything
heap->set_unload_classes(heuristics->can_unload_classes());
} else {
policy->record_explicit_to_full();
if (ShenandoahCollectorPolicy::should_run_full_gc(cause)) {
mode = stw_full;
}
} else if (implicit_gc_requested) {
cause = requested_gc_cause;
log_info(gc)("Trigger: Implicit GC request (%s)", GCCause::to_string(cause));

heuristics->record_requested_gc();

if (ShenandoahImplicitGCInvokesConcurrent) {
policy->record_implicit_to_concurrent();
} else {
mode = default_mode;

// Unload and clean up everything
heap->set_unload_classes(heuristics->can_unload_classes());
} else {
policy->record_implicit_to_full();
mode = stw_full;
}
} else {
// Potential normal cycle: ask heuristics if it wants to act
Expand All @@ -153,11 +132,11 @@ void ShenandoahControlThread::run_service() {

// Blow all soft references on this cycle, if handling allocation failure,
// either implicit or explicit GC request, or we are requested to do so unconditionally.
if (alloc_failure_pending || implicit_gc_requested || explicit_gc_requested || ShenandoahAlwaysClearSoftRefs) {
if (alloc_failure_pending || is_gc_requested || ShenandoahAlwaysClearSoftRefs) {
heap->soft_ref_policy()->set_should_clear_all_soft_refs(true);
}

bool gc_requested = (mode != none);
const bool gc_requested = (mode != none);
assert (!gc_requested || cause != GCCause::_last_gc_cause, "GC cause should be set");

if (gc_requested) {
Expand Down Expand Up @@ -193,7 +172,7 @@ void ShenandoahControlThread::run_service() {
}

// If this was the requested GC cycle, notify waiters about it
if (explicit_gc_requested || implicit_gc_requested) {
if (is_gc_requested) {
notify_gc_waiters();
}

Expand Down Expand Up @@ -266,14 +245,14 @@ void ShenandoahControlThread::run_service() {
}
}

double current = os::elapsedTime();
const double current = os::elapsedTime();

if (ShenandoahUncommit && (explicit_gc_requested || soft_max_changed || (current - last_shrink_time > shrink_period))) {
if (ShenandoahUncommit && (is_gc_requested || soft_max_changed || (current - last_shrink_time > shrink_period))) {
// Explicit GC tries to uncommit everything down to min capacity.
// Soft max change tries to uncommit everything down to target capacity.
// Periodic uncommit tries to uncommit suitable regions down to min capacity.

double shrink_before = (explicit_gc_requested || soft_max_changed) ?
double shrink_before = (is_gc_requested || soft_max_changed) ?
current :
current - (ShenandoahUncommitDelay / 1000.0);

Expand Down Expand Up @@ -395,29 +374,8 @@ void ShenandoahControlThread::service_stw_degenerated_cycle(GCCause::Cause cause
gc.collect(cause);
}

bool ShenandoahControlThread::is_explicit_gc(GCCause::Cause cause) const {
return GCCause::is_user_requested_gc(cause) ||
GCCause::is_serviceability_requested_gc(cause);
}

void ShenandoahControlThread::request_gc(GCCause::Cause cause) {
assert(GCCause::is_user_requested_gc(cause) ||
GCCause::is_serviceability_requested_gc(cause) ||
cause == GCCause::_metadata_GC_clear_soft_refs ||
cause == GCCause::_codecache_GC_aggressive ||
cause == GCCause::_codecache_GC_threshold ||
cause == GCCause::_full_gc_alot ||
cause == GCCause::_wb_young_gc ||
cause == GCCause::_wb_full_gc ||
cause == GCCause::_wb_breakpoint ||
cause == GCCause::_scavenge_alot,
"only requested GCs here: %s", GCCause::to_string(cause));

if (is_explicit_gc(cause)) {
if (!DisableExplicitGC) {
handle_requested_gc(cause);
}
} else {
if (ShenandoahCollectorPolicy::should_handle_requested_gc(cause)) {
handle_requested_gc(cause);
}
}
Expand Down
2 changes: 0 additions & 2 deletions src/hotspot/share/gc/shenandoah/shenandoahControlThread.hpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -84,8 +84,6 @@ class ShenandoahControlThread: public ConcurrentGCThread {
// Blocks until GC is over.
void handle_requested_gc(GCCause::Cause cause);

bool is_explicit_gc(GCCause::Cause cause) const;

public:
// Constructor
ShenandoahControlThread();
Expand Down
1 change: 1 addition & 0 deletions src/hotspot/share/gc/shenandoah/shenandoahUtils.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -44,6 +44,7 @@ ShenandoahGCSession::ShenandoahGCSession(GCCause::Cause cause) :
_tracer(_heap->tracer()) {
assert(!ShenandoahGCPhase::is_current_phase_valid(), "No current GC phase");

_heap->shenandoah_policy()->record_collection_cause(cause);
_heap->set_gc_cause(cause);
_timer->register_gc_start();
_tracer->report_gc_start(cause, _timer->gc_start());
Expand Down

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