Reviewers: Michael Starzinger,
Description:
Fix store buffer ensure space heuristics.
This change results in less scan on scavenge memory chunks.
BUG=
Please review this at https://codereview.chromium.org/15896037/
SVN Base: https://v8.googlecode.com/svn/branches/bleeding_edge
Affected files:
M src/store-buffer.h
M src/store-buffer.cc
Index: src/store-buffer.cc
diff --git a/src/store-buffer.cc b/src/store-buffer.cc
index
7d73dd5ed1be27464640752efc5eb5990a749b4f..1137efb54efe78993c316fd8971705c95e1aacc8
100644
--- a/src/store-buffer.cc
+++ b/src/store-buffer.cc
@@ -142,6 +142,11 @@ void StoreBuffer::Uniq() {
}
+bool StoreBuffer::SpaceAvailable(intptr_t space_needed) {
+ return old_limit_ - old_top_ >= space_needed;
+}
+
+
void StoreBuffer::EnsureSpace(intptr_t space_needed) {
while (old_limit_ - old_top_ < space_needed &&
old_limit_ < old_reserved_limit_) {
@@ -152,7 +157,7 @@ void StoreBuffer::EnsureSpace(intptr_t space_needed) {
old_limit_ += grow;
}
- if (old_limit_ - old_top_ >= space_needed) return;
+ if (SpaceAvailable(space_needed)) return;
if (old_buffer_is_filtered_) return;
ASSERT(may_move_store_buffer_entries_);
@@ -171,10 +176,7 @@ void StoreBuffer::EnsureSpace(intptr_t space_needed) {
Filter(MemoryChunk::SCAN_ON_SCAVENGE);
}
- // If filtering out the entries from scan_on_scavenge pages got us down
to
- // less than half full, then we are satisfied with that.
- if (old_limit_ - old_top_ > old_top_ - old_start_) return;
-
+ if (SpaceAvailable(space_needed)) return;
// Sample 1 entry in 97 and filter out the pages where we estimate that
more
// than 1 in 8 pointers are to new space.
static const int kSampleFinenesses = 5;
@@ -188,11 +190,11 @@ void StoreBuffer::EnsureSpace(intptr_t space_needed) {
{ 3, ((Page::kPageSize / kPointerSize) / 3) / 256 },
{ 1, 0}
};
- for (int i = kSampleFinenesses - 1; i >= 0; i--) {
+ for (int i = 0; i < kSampleFinenesses; i++) {
ExemptPopularPages(samples[i].prime_sample_step, samples[i].threshold);
// As a last resort we mark all pages as being exempt from the store
buffer.
ASSERT(i != 0 || old_top_ == old_start_);
- if (old_limit_ - old_top_ > old_top_ - old_start_) return;
+ if (SpaceAvailable(space_needed)) return;
}
UNREACHABLE();
}
Index: src/store-buffer.h
diff --git a/src/store-buffer.h b/src/store-buffer.h
index
514534a1ed72c5af95827ffd3926ad90f497e976..4ecc43b5276dcf8ad1a8835de0b52c79075a4475
100644
--- a/src/store-buffer.h
+++ b/src/store-buffer.h
@@ -111,6 +111,7 @@ class StoreBuffer {
// been promoted. Rebuilds the store buffer completely if it overflowed.
void SortUniq();
+ bool SpaceAvailable(intptr_t space_needed);
void EnsureSpace(intptr_t space_needed);
void Verify();
--
--
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