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6362677: Change parallel GC collector default number of parallel GC threads
Use the same default number of GC threads as used by ParNewGC and ConcMarkSweepGC (i.e., the 5/8th rule). Reviewed-by: ysr, tonyp
This commit is contained in:
Jon Masamitsu
parent
74f243990c
commit
63f1de52fc
8 changed files with 174 additions and 81 deletions
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@ -924,10 +924,18 @@ static void no_shared_spaces() {
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void Arguments::set_parnew_gc_flags() {
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assert(!UseSerialGC && !UseParallelGC, "control point invariant");
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// Turn off AdaptiveSizePolicy by default for parnew until it is
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// complete.
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if (UseParNewGC &&
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FLAG_IS_DEFAULT(UseAdaptiveSizePolicy)) {
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FLAG_SET_DEFAULT(UseAdaptiveSizePolicy, false);
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}
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if (FLAG_IS_DEFAULT(UseParNewGC) && ParallelGCThreads > 1) {
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FLAG_SET_DEFAULT(UseParNewGC, true);
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} else if (UseParNewGC && ParallelGCThreads == 0) {
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FLAG_SET_DEFAULT(ParallelGCThreads, nof_parallel_gc_threads());
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FLAG_SET_DEFAULT(ParallelGCThreads,
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Abstract_VM_Version::parallel_worker_threads());
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if (FLAG_IS_DEFAULT(ParallelGCThreads) && ParallelGCThreads == 1) {
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FLAG_SET_DEFAULT(UseParNewGC, false);
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}
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@ -956,25 +964,6 @@ void Arguments::set_parnew_gc_flags() {
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}
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}
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// CAUTION: this code is currently shared by UseParallelGC, UseParNewGC and
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// UseconcMarkSweepGC. Further tuning of individual collectors might
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// dictate refinement on a per-collector basis.
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int Arguments::nof_parallel_gc_threads() {
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if (FLAG_IS_DEFAULT(ParallelGCThreads)) {
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// For very large machines, there are diminishing returns
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// for large numbers of worker threads. Instead of
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// hogging the whole system, use 5/8ths of a worker for every
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// processor after the first 8. For example, on a 72 cpu
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// machine use 8 + (72 - 8) * (5/8) == 48 worker threads.
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// This is just a start and needs further tuning and study in
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// Tiger.
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int ncpus = os::active_processor_count();
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return (ncpus <= 8) ? ncpus : 3 + ((ncpus * 5) / 8);
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} else {
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return ParallelGCThreads;
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}
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}
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// Adjust some sizes to suit CMS and/or ParNew needs; these work well on
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// sparc/solaris for certain applications, but would gain from
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// further optimization and tuning efforts, and would almost
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@ -984,26 +973,24 @@ void Arguments::set_cms_and_parnew_gc_flags() {
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return;
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}
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assert(UseConcMarkSweepGC, "CMS is expected to be on here");
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// If we are using CMS, we prefer to UseParNewGC,
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// unless explicitly forbidden.
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if (UseConcMarkSweepGC && !UseParNewGC && FLAG_IS_DEFAULT(UseParNewGC)) {
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FLAG_SET_DEFAULT(UseParNewGC, true);
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if (!UseParNewGC && FLAG_IS_DEFAULT(UseParNewGC)) {
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FLAG_SET_ERGO(bool, UseParNewGC, true);
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}
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// Turn off AdaptiveSizePolicy by default for cms until it is
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// complete. Also turn it off in general if the
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// parnew collector has been selected.
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if ((UseConcMarkSweepGC || UseParNewGC) &&
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FLAG_IS_DEFAULT(UseAdaptiveSizePolicy)) {
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// complete.
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if (FLAG_IS_DEFAULT(UseAdaptiveSizePolicy)) {
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FLAG_SET_DEFAULT(UseAdaptiveSizePolicy, false);
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}
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// In either case, adjust ParallelGCThreads and/or UseParNewGC
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// as needed.
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set_parnew_gc_flags();
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if (!UseConcMarkSweepGC) {
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return;
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if (UseParNewGC) {
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set_parnew_gc_flags();
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}
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// Now make adjustments for CMS
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@ -1147,17 +1134,11 @@ void Arguments::set_ergonomics_flags() {
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FLAG_IS_DEFAULT(UseParallelGC)) {
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if (should_auto_select_low_pause_collector()) {
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FLAG_SET_ERGO(bool, UseConcMarkSweepGC, true);
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set_cms_and_parnew_gc_flags();
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} else {
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FLAG_SET_ERGO(bool, UseParallelGC, true);
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}
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no_shared_spaces();
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}
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// This is here because the parallel collector could
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// have been selected so this initialization should
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// still be done.
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set_parallel_gc_flags();
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}
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}
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@ -1170,6 +1151,9 @@ void Arguments::set_parallel_gc_flags() {
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// If no heap maximum was requested explicitly, use some reasonable fraction
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// of the physical memory, up to a maximum of 1GB.
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if (UseParallelGC) {
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FLAG_SET_ERGO(uintx, ParallelGCThreads,
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Abstract_VM_Version::parallel_worker_threads());
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if (FLAG_IS_DEFAULT(MaxHeapSize)) {
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const uint64_t reasonable_fraction =
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os::physical_memory() / DefaultMaxRAMFraction;
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@ -1312,6 +1296,31 @@ static bool verify_serial_gc_flags() {
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UseParallelOldGC));
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}
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// Check consistency of GC selection
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bool Arguments::check_gc_consistency() {
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bool status = true;
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// Ensure that the user has not selected conflicting sets
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// of collectors. [Note: this check is merely a user convenience;
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// collectors over-ride each other so that only a non-conflicting
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// set is selected; however what the user gets is not what they
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// may have expected from the combination they asked for. It's
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// better to reduce user confusion by not allowing them to
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// select conflicting combinations.
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uint i = 0;
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if (UseSerialGC) i++;
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if (UseConcMarkSweepGC || UseParNewGC) i++;
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if (UseParallelGC || UseParallelOldGC) i++;
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if (i > 1) {
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jio_fprintf(defaultStream::error_stream(),
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"Conflicting collector combinations in option list; "
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"please refer to the release notes for the combinations "
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"allowed\n");
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status = false;
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}
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return status;
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}
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// Check the consistency of vm_init_args
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bool Arguments::check_vm_args_consistency() {
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// Method for adding checks for flag consistency.
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@ -1354,14 +1363,14 @@ bool Arguments::check_vm_args_consistency() {
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status = false;
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}
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status &= verify_percentage(MaxLiveObjectEvacuationRatio,
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status = status && verify_percentage(MaxLiveObjectEvacuationRatio,
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"MaxLiveObjectEvacuationRatio");
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status &= verify_percentage(AdaptiveSizePolicyWeight,
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status = status && verify_percentage(AdaptiveSizePolicyWeight,
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"AdaptiveSizePolicyWeight");
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status &= verify_percentage(AdaptivePermSizeWeight, "AdaptivePermSizeWeight");
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status &= verify_percentage(ThresholdTolerance, "ThresholdTolerance");
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status &= verify_percentage(MinHeapFreeRatio, "MinHeapFreeRatio");
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status &= verify_percentage(MaxHeapFreeRatio, "MaxHeapFreeRatio");
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status = status && verify_percentage(AdaptivePermSizeWeight, "AdaptivePermSizeWeight");
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status = status && verify_percentage(ThresholdTolerance, "ThresholdTolerance");
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status = status && verify_percentage(MinHeapFreeRatio, "MinHeapFreeRatio");
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status = status && verify_percentage(MaxHeapFreeRatio, "MaxHeapFreeRatio");
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if (MinHeapFreeRatio > MaxHeapFreeRatio) {
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jio_fprintf(defaultStream::error_stream(),
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@ -1377,14 +1386,14 @@ bool Arguments::check_vm_args_consistency() {
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MarkSweepAlwaysCompactCount = 1; // Move objects every gc.
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}
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status &= verify_percentage(GCHeapFreeLimit, "GCHeapFreeLimit");
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status &= verify_percentage(GCTimeLimit, "GCTimeLimit");
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status = status && verify_percentage(GCHeapFreeLimit, "GCHeapFreeLimit");
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status = status && verify_percentage(GCTimeLimit, "GCTimeLimit");
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if (GCTimeLimit == 100) {
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// Turn off gc-overhead-limit-exceeded checks
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FLAG_SET_DEFAULT(UseGCOverheadLimit, false);
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}
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status &= verify_percentage(GCHeapFreeLimit, "GCHeapFreeLimit");
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status = status && verify_percentage(GCHeapFreeLimit, "GCHeapFreeLimit");
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// Check user specified sharing option conflict with Parallel GC
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bool cannot_share = (UseConcMarkSweepGC || UseParallelGC ||
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@ -1402,24 +1411,7 @@ bool Arguments::check_vm_args_consistency() {
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}
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}
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// Ensure that the user has not selected conflicting sets
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// of collectors. [Note: this check is merely a user convenience;
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// collectors over-ride each other so that only a non-conflicting
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// set is selected; however what the user gets is not what they
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// may have expected from the combination they asked for. It's
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// better to reduce user confusion by not allowing them to
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// select conflicting combinations.
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uint i = 0;
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if (UseSerialGC) i++;
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if (UseConcMarkSweepGC || UseParNewGC) i++;
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if (UseParallelGC || UseParallelOldGC) i++;
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if (i > 1) {
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jio_fprintf(defaultStream::error_stream(),
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"Conflicting collector combinations in option list; "
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"please refer to the release notes for the combinations "
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"allowed\n");
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status = false;
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}
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status = status && check_gc_consistency();
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if (_has_alloc_profile) {
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if (UseParallelGC || UseParallelOldGC) {
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@ -1451,15 +1443,15 @@ bool Arguments::check_vm_args_consistency() {
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"allocation buffers\n(-XX:+UseTLAB).\n");
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status = false;
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} else {
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status &= verify_percentage(CMSIncrementalDutyCycle,
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status = status && verify_percentage(CMSIncrementalDutyCycle,
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"CMSIncrementalDutyCycle");
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status &= verify_percentage(CMSIncrementalDutyCycleMin,
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status = status && verify_percentage(CMSIncrementalDutyCycleMin,
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"CMSIncrementalDutyCycleMin");
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status &= verify_percentage(CMSIncrementalSafetyFactor,
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status = status && verify_percentage(CMSIncrementalSafetyFactor,
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"CMSIncrementalSafetyFactor");
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status &= verify_percentage(CMSIncrementalOffset,
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status = status && verify_percentage(CMSIncrementalOffset,
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"CMSIncrementalOffset");
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status &= verify_percentage(CMSExpAvgFactor,
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status = status && verify_percentage(CMSExpAvgFactor,
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"CMSExpAvgFactor");
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// If it was not set on the command line, set
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// CMSInitiatingOccupancyFraction to 1 so icms can initiate cycles early.
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@ -2064,7 +2056,8 @@ jint Arguments::parse_each_vm_init_arg(const JavaVMInitArgs* args,
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// Enable parallel GC and adaptive generation sizing
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FLAG_SET_CMDLINE(bool, UseParallelGC, true);
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FLAG_SET_DEFAULT(ParallelGCThreads, nof_parallel_gc_threads());
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FLAG_SET_DEFAULT(ParallelGCThreads,
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Abstract_VM_Version::parallel_worker_threads());
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// Encourage steady state memory management
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FLAG_SET_CMDLINE(uintx, ThresholdTolerance, 100);
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@ -2451,15 +2444,25 @@ jint Arguments::parse(const JavaVMInitArgs* args) {
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no_shared_spaces();
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#endif // KERNEL
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// Set some flags for ParallelGC if needed.
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set_parallel_gc_flags();
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// Set some flags for CMS and/or ParNew collectors, as needed.
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set_cms_and_parnew_gc_flags();
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// Set flags based on ergonomics.
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set_ergonomics_flags();
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// Check the GC selections again.
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if (!check_gc_consistency()) {
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return JNI_EINVAL;
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}
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if (UseParallelGC) {
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// Set some flags for ParallelGC if needed.
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set_parallel_gc_flags();
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} else if (UseConcMarkSweepGC) {
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// Set some flags for CMS
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set_cms_and_parnew_gc_flags();
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} else if (UseParNewGC) {
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// Set some flags for ParNew
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set_parnew_gc_flags();
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}
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#ifdef SERIALGC
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assert(verify_serial_gc_flags(), "SerialGC unset");
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#endif // SERIALGC
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@ -2479,6 +2482,12 @@ jint Arguments::parse(const JavaVMInitArgs* args) {
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CommandLineFlags::printSetFlags();
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}
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#ifdef ASSERT
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if (PrintFlagsFinal) {
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CommandLineFlags::printFlags();
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}
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#endif
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return JNI_OK;
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}
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