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Eliminate an unnecessary clock check for unsampled trackers. #716

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Eliminate an unnecessary clock check for unsampled trackers. #716

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4 changes: 2 additions & 2 deletions tcmalloc/huge_page_filler.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1233,11 +1233,11 @@ HugePageFiller<TrackerType>::TryGet(Length n, SpanAllocInfo span_alloc_info) {
TC_ASSERT(type == AccessDensityPrediction::kSparse || pt->HasDenseSpans());

// Log previous features before modifying the page tracker.
const auto now = clock_.now();
if (pt->GetTagState().sampled_for_tagging) {
const auto now = clock_.now();
pt->RecordFeatures();
pt->SetLastAllocationTime(now);
}
pt->SetLastAllocationTime(now);
const auto page_allocation = pt->Get(n, span_alloc_info);
AddToFillerList(pt);
pages_allocated_[type] += n;
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39 changes: 38 additions & 1 deletion tcmalloc/huge_page_filler_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -714,7 +714,7 @@ TEST_F(FillerTest, ClockCalls) {
page2 = res.page;
}
EXPECT_EQ(alloc_pt, pt);
EXPECT_EQ(FakeClock::now_calls(), 2);
EXPECT_EQ(FakeClock::now_calls(), 1);
EXPECT_EQ(FakeClock::freq_calls(), 0);

// 3. Put (partially freed hugepage).
Expand All @@ -741,6 +741,43 @@ TEST_F(FillerTest, ClockCalls) {
EXPECT_EQ(FakeClock::now_calls(), 2);
EXPECT_EQ(FakeClock::freq_calls(), 1);

// 5. Contribute and wait for pt to be sampled.
while (true) {
PageHeapSpinLockHolder l;
page1 = pt->Get(Length(1), info).page;
filler_.Contribute(pt, /*donated=*/false, info);
if (pt->GetTagState().sampled_for_tagging) {
break;
}
filler_.Put(pt, Range(page1, Length(1)), info);
}

FakeClock::ResetCalls();

{
PageHeapSpinLockHolder l;
auto res = filler_.TryGet(Length(1), info);
alloc_pt = res.pt;
page2 = res.page;
}

EXPECT_EQ(alloc_pt, pt);
EXPECT_EQ(FakeClock::now_calls(), 2);
EXPECT_EQ(FakeClock::freq_calls(), 0);

FakeClock::ResetCalls();

{
PageHeapSpinLockHolder l;
put_res1 = filler_.Put(alloc_pt, Range(page2, Length(1)), info);
put_res2 = filler_.Put(pt, Range(page1, Length(1)), info);
}

EXPECT_EQ(put_res1, nullptr);
EXPECT_EQ(put_res2, pt);
EXPECT_EQ(FakeClock::now_calls(), 3);
EXPECT_EQ(FakeClock::freq_calls(), 1);

delete pt;
}

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