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6362677: Change parallel GC collector default number of parallel GC threads

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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 2008-02-22 17:17:14 -08:00
parent 74f243990c
commit 63f1de52fc
8 changed files with 174 additions and 81 deletions
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42
hotspot/src/share/vm/runtime/vm_version.cpp
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@ -52,6 +52,8 @@ int Abstract_VM_Version::_vm_major_version = 0;
int Abstract_VM_Version::_vm_minor_version = 0;
int Abstract_VM_Version::_vm_build_number = 0;
bool Abstract_VM_Version::_initialized = false;
int Abstract_VM_Version::_parallel_worker_threads = 0;
bool Abstract_VM_Version::_parallel_worker_threads_initialized = false;
void Abstract_VM_Version::initialize() {
if (_initialized) {
@ -210,3 +212,43 @@ void VM_Version_init() {
}
#endif
}
unsigned int Abstract_VM_Version::nof_parallel_worker_threads(
unsigned int num,
unsigned int den,
unsigned int switch_pt) {
if (FLAG_IS_DEFAULT(ParallelGCThreads)) {
assert(ParallelGCThreads == 0, "Default ParallelGCThreads is not 0");
// For very large machines, there are diminishing returns
// for large numbers of worker threads. Instead of
// hogging the whole system, use a fraction of the workers for every
// processor after the first 8. For example, on a 72 cpu machine
// and a chosen fraction of 5/8
// use 8 + (72 - 8) * (5/8) == 48 worker threads.
unsigned int ncpus = (unsigned int) os::active_processor_count();
return (ncpus <= switch_pt) ?
ncpus :
(switch_pt + ((ncpus - switch_pt) * num) / den);
} else {
return ParallelGCThreads;
}
}
unsigned int Abstract_VM_Version::calc_parallel_worker_threads() {
return nof_parallel_worker_threads(5, 8, 8);
}
// Does not set the _initialized flag since it is
// a global flag.
unsigned int Abstract_VM_Version::parallel_worker_threads() {
if (!_parallel_worker_threads_initialized) {
if (FLAG_IS_DEFAULT(ParallelGCThreads)) {
_parallel_worker_threads = VM_Version::calc_parallel_worker_threads();
} else {
_parallel_worker_threads = ParallelGCThreads;
}
_parallel_worker_threads_initialized = true;
}
return _parallel_worker_threads;
}