Disable parallel GC by default
Not using parallel GC seems to reduce avg pauses by ~0.1s on
EvaluateAndApplyChanges. Avoiding creating the thread pool should
help app launch slightly and reduce memory ussage.
Change-Id: Iebec2a17701c76e4145b41d7c0b4f6dd17806efa
diff --git a/runtime/gc/collector/mark_sweep.cc b/runtime/gc/collector/mark_sweep.cc
index bb8d876..e65d1f1 100644
--- a/runtime/gc/collector/mark_sweep.cc
+++ b/runtime/gc/collector/mark_sweep.cc
@@ -740,11 +740,7 @@
if (heap_->GetThreadPool() == nullptr || !heap_->CareAboutPauseTimes()) {
return 1;
}
- if (paused) {
- return heap_->GetParallelGCThreadCount() + 1;
- } else {
- return heap_->GetConcGCThreadCount() + 1;
- }
+ return (paused ? heap_->GetParallelGCThreadCount() : heap_->GetConcGCThreadCount()) + 1;
}
void MarkSweep::ScanGrayObjects(bool paused, uint8_t minimum_age) {
diff --git a/runtime/gc/heap.h b/runtime/gc/heap.h
index 2f62798..066b4c5 100644
--- a/runtime/gc/heap.h
+++ b/runtime/gc/heap.h
@@ -145,6 +145,8 @@
static constexpr double kDefaultHeapGrowthMultiplier = 2.0;
// Primitive arrays larger than this size are put in the large object space.
static constexpr size_t kDefaultLargeObjectThreshold = 3 * kPageSize;
+ // Whether or not parallel GC is enabled. If not, then we never create the thread pool.
+ static constexpr bool kDefaultEnableParallelGC = false;
// Whether or not we use the free list large object space. Only use it if USE_ART_LOW_4G_ALLOCATOR
// since this means that we have to use the slow msync loop in MemMap::MapAnonymous.
diff --git a/runtime/parsed_options.cc b/runtime/parsed_options.cc
index c23f744..8567b44 100644
--- a/runtime/parsed_options.cc
+++ b/runtime/parsed_options.cc
@@ -440,8 +440,8 @@
}
// Default to number of processors minus one since the main GC thread also does work.
- args.SetIfMissing(M::ParallelGCThreads,
- static_cast<unsigned int>(sysconf(_SC_NPROCESSORS_CONF) - 1u));
+ args.SetIfMissing(M::ParallelGCThreads, gc::Heap::kDefaultEnableParallelGC ?
+ static_cast<unsigned int>(sysconf(_SC_NPROCESSORS_CONF) - 1u) : 0u);
// -Xverbose:
{
diff --git a/runtime/runtime_options.def b/runtime/runtime_options.def
index 339f925..e420d52 100644
--- a/runtime/runtime_options.def
+++ b/runtime/runtime_options.def
@@ -50,7 +50,7 @@
RUNTIME_OPTIONS_KEY (MemoryKiB, NonMovingSpaceCapacity, gc::Heap::kDefaultNonMovingSpaceCapacity)
RUNTIME_OPTIONS_KEY (double, HeapTargetUtilization, gc::Heap::kDefaultTargetUtilization)
RUNTIME_OPTIONS_KEY (double, ForegroundHeapGrowthMultiplier, gc::Heap::kDefaultHeapGrowthMultiplier)
-RUNTIME_OPTIONS_KEY (unsigned int, ParallelGCThreads, 1u)
+RUNTIME_OPTIONS_KEY (unsigned int, ParallelGCThreads, 0u)
RUNTIME_OPTIONS_KEY (unsigned int, ConcGCThreads)
RUNTIME_OPTIONS_KEY (Memory<1>, StackSize) // -Xss
RUNTIME_OPTIONS_KEY (unsigned int, MaxSpinsBeforeThinLockInflation,Monitor::kDefaultMaxSpinsBeforeThinLockInflation)