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Fix pagemap root residency adjustment in metadata_bytes. #541

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Fix pagemap root residency adjustment in metadata_bytes. #541

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4 changes: 2 additions & 2 deletions tcmalloc/global_stats.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -182,8 +182,8 @@ void ExtractStats(TCMallocStats& r, uint64_t* absl_nullable class_count,
if (report_residence) {
auto resident_bytes = tc_globals.pagemap_residence();
r.pagemap_root_bytes_res = resident_bytes;
TC_ASSERT_GE(r.metadata_bytes, r.pagemap_bytes);
r.metadata_bytes = r.metadata_bytes - r.pagemap_bytes + resident_bytes;
TC_ASSERT_GE(r.metadata_bytes, sizeof(PageMap));
r.metadata_bytes = r.metadata_bytes - sizeof(PageMap) + resident_bytes;
} else {
r.pagemap_root_bytes_res = 0;
}
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45 changes: 45 additions & 0 deletions tcmalloc/stats_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -24,9 +24,12 @@
#include "absl/base/internal/cycleclock.h"
#include "absl/time/clock.h"
#include "absl/time/time.h"
#include "tcmalloc/global_stats.h"
#include "tcmalloc/huge_pages.h"
#include "tcmalloc/internal/logging.h"
#include "tcmalloc/pagemap.h"
#include "tcmalloc/pages.h"
#include "tcmalloc/static_vars.h"
#include "tcmalloc/testing/testutil.h"

namespace tcmalloc {
Expand Down Expand Up @@ -177,6 +180,48 @@ TEST(ClockTest, ClockTicks) {
EXPECT_GE(actual * 1.01, measured) << actual;
}

TEST(GlobalStatsTest, PageMapMemoryAccounted) {
TCMallocStats before;
ExtractTCMallocStats(before, /*report_residence=*/true);
const size_t pagemap_bytes_before = []() {
PageHeapSpinLockHolder l;
return tc_globals.pagemap().bytes();
}();

// Ensure several distant pages that require allocating new internal and leaf
// nodes in the PageMap radix tree.
const PageId p1{100000000};
const PageId p2{200000000};
{
PageHeapSpinLockHolder l;
ASSERT_TRUE(tc_globals.pagemap().Ensure(Range(p1, Length(1))));
ASSERT_TRUE(tc_globals.pagemap().Ensure(Range(p2, Length(1))));
}
const size_t pagemap_bytes_after = []() {
PageHeapSpinLockHolder l;
return tc_globals.pagemap().bytes();
}();
ASSERT_GT(pagemap_bytes_after, pagemap_bytes_before);
const size_t pagemap_increase = pagemap_bytes_after - pagemap_bytes_before;

TCMallocStats after;
ExtractTCMallocStats(after, /*report_residence=*/true);

// Metadata bytes must properly account for newly allocated pagemap
// nodes/leaves.
EXPECT_GE(after.metadata_bytes, before.metadata_bytes + pagemap_increase);

TCMallocStats without_residence;
ExtractTCMallocStats(without_residence, /*report_residence=*/false);

// The difference in metadata bytes between reporting residence or not should
// only reflect unresident portions of the pagemap root and per-CPU slabs,
// not the entire pagemap dynamically allocated memory.
EXPECT_GE(after.metadata_bytes, without_residence.metadata_bytes -
sizeof(PageMap) -
after.percpu_metadata_bytes);
}

} // namespace
} // namespace tcmalloc_internal
} // namespace tcmalloc
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