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copybara-service merged 1 commit into from
Aug 11, 2026
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Print low water mark in HugeRegion to telemetry. #482

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7 changes: 4 additions & 3 deletions docs/stats.md
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Original file line number Diff line number Diff line change
Expand Up @@ -833,7 +833,7 @@ contain multiple regions.
```
HugeRegionSet: 1 MiB+ allocations best-fit into 1024 MiB slabs
HugeRegionSet: 0 total regions
HugeRegionSet: 0 hugepages backed out of 0 total
HugeRegionSet: 0 hugepages backed, 0 backed and free, 0 low water mark free backed, out of 0 total
HugeRegionSet: 0 pages free in backed region, 0.0000 free
```

Expand All @@ -842,8 +842,9 @@ The lines of output indicate:
* The size of each region in MiB - this is currently 1GiB.
* The total number of regions in the region cache, in the example above there
are no regions in the cache.
* The number of backed hugepages in the cache out of the total number of
hugepages in the region cache.
* The number of backed hugepages in the cache, backed and free, the low water
mark of free backed pages, out of the total number of hugepages in the
region cache.
* The number of free TCMalloc pages in the regions, and as a ratio of the
number of backed pages.

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6 changes: 4 additions & 2 deletions tcmalloc/huge_region.h
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Expand Up @@ -656,9 +656,9 @@ inline void HugeRegionSet<Region>::Print(Printer& out) const {

out.printf(
"HugeRegionSet: %zu hugepages backed, %zu backed and free, "
"out of %zu total\n",
"%zu low water mark free backed, out of %zu total\n",
total_backed.raw_num(), total_free_backed.raw_num(),
Region::size().raw_num() * n_);
lowater_free_backed_.raw_num(), Region::size().raw_num() * n_);

const Length in_pages = total_backed.in_pages();
out.printf("HugeRegionSet: %zu pages free in backed region, %.4f free\n",
Expand All @@ -672,6 +672,8 @@ template <typename Region>
inline void HugeRegionSet<Region>::PrintInPbtxt(PbtxtRegion& hpaa) const {
hpaa.PrintI64("min_huge_region_alloc_size", 1024 * 1024);
hpaa.PrintI64("huge_region_size", Region::size().in_bytes());
hpaa.PrintI64("huge_region_low_water_mark_bytes",
lowater_free_backed_.in_bytes());
for (Region* region : list_) {
auto detail = hpaa.CreateSubRegion("huge_region_details");
region->PrintInPbtxt(detail);
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9 changes: 9 additions & 0 deletions tcmalloc/huge_region_test.cc
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Expand Up @@ -1128,6 +1128,15 @@ TEST_P(HugeRegionSetTest, Set) {
Printer out(&buf[0], buf.size());
set_.Print(out);
printf("%s\n", &buf[0]);
EXPECT_THAT(absl::string_view(&buf[0]),
testing::HasSubstr("0 low water mark free backed"));

std::vector<char> pbtxt_buf(64 * 1024);
Printer pbtxt_out(&pbtxt_buf[0], pbtxt_buf.size());
PbtxtRegion region(pbtxt_out, kNested);
set_.PrintInPbtxt(region);
EXPECT_THAT(absl::string_view(&pbtxt_buf[0]),
testing::HasSubstr("huge_region_low_water_mark_bytes: 0"));
}

TEST(HugeRegionNamedVmaTest, NamedVmaNormal) {
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