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Retire pow2 below 64 reuse size classes, replace with relaxed size classes #627

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Merged
copybara-service merged 1 commit into from
Sep 1, 2026
Merged

Retire pow2 below 64 reuse size classes, replace with relaxed size classes #627

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1 change: 0 additions & 1 deletion tcmalloc/BUILD
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Expand Up @@ -223,7 +223,6 @@ create_tcmalloc_libraries(
"pagemap.h",
"parameters.cc",
"peak_heap_tracker.cc",
"reuse_relaxed_below_64_size_classes.cc",
"sampler.cc",
"sampler.h",
"segv_handler.cc",
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1 change: 0 additions & 1 deletion tcmalloc/CMakeLists.txt
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Expand Up @@ -278,7 +278,6 @@ tcmalloc_cc_library_variants(
"pagemap.h"
"parameters.cc"
"peak_heap_tracker.cc"
"reuse_relaxed_below_64_size_classes.cc"
"sampler.cc"
"sampler.h"
"segv_handler.cc"
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4 changes: 1 addition & 3 deletions tcmalloc/cpu_cache.h
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Expand Up @@ -154,9 +154,7 @@ class StaticForwarder : private Parameters {

bool reuse_size_classes() const {
return state_.size_class_configuration() ==
SizeClassConfiguration::kReuse ||
state_.size_class_configuration() ==
SizeClassConfiguration::kReuseRelaxedBelow64;
SizeClassConfiguration::kReuseRelaxedBelow64;
}

size_t class_to_size(int size_class) const {
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2 changes: 0 additions & 2 deletions tcmalloc/global_stats.cc
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Expand Up @@ -277,8 +277,6 @@ static absl::string_view SizeClassConfigurationString(
case SizeClassConfiguration::kLegacy:
// TODO(b/242710633): remove this opt out.
return "SIZE_CLASS_LEGACY";
case SizeClassConfiguration::kReuse:
return "SIZE_CLASS_REUSE";
case SizeClassConfiguration::kReuseRelaxedBelow64:
return "SIZE_CLASS_REUSE_RELAXED_BELOW_64";
}
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522 changes: 0 additions & 522 deletions tcmalloc/reuse_relaxed_below_64_size_classes.cc
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This file was deleted.

465 changes: 234 additions & 231 deletions tcmalloc/size_classes.cc
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1 change: 0 additions & 1 deletion tcmalloc/size_classes_test.cc
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Expand Up @@ -182,7 +182,6 @@ TEST_F(RunTimeSizeClassesTest, WastedSpan) {
// (alignment) at the end of the span.
switch (tc_globals.size_class_configuration()) {
case SizeClassConfiguration::kLegacy:
case SizeClassConfiguration::kReuse:
case SizeClassConfiguration::kReuseRelaxedBelow64:
// This test fails for other classes (was passing with a different span
// size allocation algorithm used between cl/130150125 and cl/139955211).
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3 changes: 0 additions & 3 deletions tcmalloc/sizemap.cc
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Expand Up @@ -46,9 +46,6 @@ const SizeClasses& SizeMap::CurrentClasses() {
case SizeClassConfiguration::kPow2Only:
return kExperimentalPow2SizeClasses;
case SizeClassConfiguration::kReuseRelaxedBelow64:
return kReuseRelaxedBelow64SizeClasses;
case SizeClassConfiguration::kReuse:
// TODO(b/512895228): remove this opt out once we are done experimenting.
return kSizeClasses;
case SizeClassConfiguration::kLegacy:
// TODO(b/242710633): remove this opt out.
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2 changes: 0 additions & 2 deletions tcmalloc/sizemap.h
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Expand Up @@ -44,12 +44,10 @@ extern const SizeClasses kSizeClasses;
// Experimental size classes:
extern const SizeClasses kExperimentalPow2SizeClasses;
extern const SizeClasses kLegacySizeClasses;
extern const SizeClasses kReuseRelaxedBelow64SizeClasses;

enum class SizeClassConfiguration {
kPow2Only = 2,
kLegacy = 4,
kReuse = 6,
kReuseRelaxedBelow64 = 8,
};

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14 changes: 2 additions & 12 deletions tcmalloc/sizemap_test.cc
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Expand Up @@ -86,7 +86,6 @@ TEST(ColdSizeClassTest, ColdFeatureActivation) {
const SizeClasses* const kAllSizeClassesConfigs[] = {
&kSizeClasses,
&kLegacySizeClasses,
&kReuseRelaxedBelow64SizeClasses,
&kExperimentalPow2SizeClasses,
};

Expand Down Expand Up @@ -266,10 +265,10 @@ TEST(SizeMapTest, HeapPartitioningSizeZero) {
}

TEST(SizeMapTest, SpecificClassRanges) {
// Verify kReuseRelaxedBelow64SizeClasses (with 24/48)
// Verify kSizeClasses (with 24/48)
{
SizeMap size_map;
ASSERT_TRUE(size_map.Init(kReuseRelaxedBelow64SizeClasses.classes));
ASSERT_TRUE(size_map.Init(kSizeClasses.classes));
EXPECT_THAT(size_map.class_to_size_range(1), Pair(1, 8));
EXPECT_THAT(size_map.class_to_size_range(2), Pair(9, 16));
#if defined(__cpp_aligned_new) && __STDCPP_DEFAULT_NEW_ALIGNMENT__ <= 8
Expand All @@ -284,15 +283,6 @@ TEST(SizeMapTest, SpecificClassRanges) {
#endif
}

// Verify kSizeClasses (default, power of two below 64)
{
SizeMap size_map;
ASSERT_TRUE(size_map.Init(kSizeClasses.classes));
EXPECT_THAT(size_map.class_to_size_range(1), Pair(1, 8));
EXPECT_THAT(size_map.class_to_size_range(2), Pair(9, 16));
EXPECT_THAT(size_map.class_to_size_range(3), Pair(17, 32));
EXPECT_THAT(size_map.class_to_size_range(4), Pair(33, 64));
}
}

} // namespace tcmalloc::tcmalloc_internal
5 changes: 0 additions & 5 deletions tcmalloc/static_vars.cc
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Expand Up @@ -171,15 +171,10 @@ SizeClassConfiguration Static::size_class_configuration() {
const char* e_reuse = thread_safe_getenv("TCMALLOC_REUSE_SIZE_CLASSES");
const char* e_legacy = thread_safe_getenv("TCMALLOC_LEGACY_SIZE_CLASSES");

if (IsExperimentActive(Experiment::TCMALLOC_REUSE_SIZE_CLASSES_ABLATION)) {
return SizeClassConfiguration::kReuse;
}

if (e_reuse != nullptr) {
if (!strcmp(e_reuse, "reuserelaxedbelow64")) {
return SizeClassConfiguration::kReuseRelaxedBelow64;
} else if (!strcmp(e_reuse, "reuse")) {
return SizeClassConfiguration::kReuse;
} else if (!strcmp(e_reuse, "0")) {
// "0" is a valid value that falls back to the default.
} else {
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16 changes: 0 additions & 16 deletions tcmalloc/tcmalloc_variants.cmake
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Expand Up @@ -203,22 +203,6 @@ function(tcmalloc_cc_test_variants)
DEPS ${TCMALLOC_DEPS} $<LINK_LIBRARY:WHOLE_ARCHIVE,tcmalloc::tcmalloc,tcmalloc::common_8k_pages,tcmalloc::want_legacy_size_classes>
)
set_tests_properties(${TCMALLOC_NAME}_legacy_size_classes PROPERTIES ENVIRONMENT "TEST_TMPDIR=${CMAKE_CURRENT_BINARY_DIR};TEST_SRCDIR=${CMAKE_SOURCE_DIR}")
tcmalloc_cc_test(NAME ${TCMALLOC_NAME}_reuse_size_classes
SRCS ${TCMALLOC_SRCS}
HDRS ${TCMALLOC_HDRS}
COPTS ${TCMALLOC_COPTS}
LINKOPTS ${TCMALLOC_LINKOPTS}
DEPS ${TCMALLOC_DEPS} $<LINK_LIBRARY:WHOLE_ARCHIVE,tcmalloc::tcmalloc,tcmalloc::common_8k_pages>
)
set_tests_properties(${TCMALLOC_NAME}_reuse_size_classes PROPERTIES ENVIRONMENT "TCMALLOC_REUSE_SIZE_CLASSES=reuse;TEST_TMPDIR=${CMAKE_CURRENT_BINARY_DIR};TEST_SRCDIR=${CMAKE_SOURCE_DIR}")
tcmalloc_cc_test(NAME ${TCMALLOC_NAME}_reuserelaxedbelow64_size_classes
SRCS ${TCMALLOC_SRCS}
HDRS ${TCMALLOC_HDRS}
COPTS ${TCMALLOC_COPTS}
LINKOPTS ${TCMALLOC_LINKOPTS}
DEPS ${TCMALLOC_DEPS} $<LINK_LIBRARY:WHOLE_ARCHIVE,tcmalloc::tcmalloc,tcmalloc::common_8k_pages>
)
set_tests_properties(${TCMALLOC_NAME}_reuserelaxedbelow64_size_classes PROPERTIES ENVIRONMENT "TCMALLOC_REUSE_SIZE_CLASSES=reuserelaxedbelow64;TEST_TMPDIR=${CMAKE_CURRENT_BINARY_DIR};TEST_SRCDIR=${CMAKE_SOURCE_DIR}")
tcmalloc_cc_test(NAME ${TCMALLOC_NAME}_hpaa
SRCS ${TCMALLOC_SRCS}
HDRS ${TCMALLOC_HDRS}
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16 changes: 0 additions & 16 deletions tcmalloc/variants.bzl
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Expand Up @@ -183,22 +183,6 @@ test_variants = [
],
"copts": [],
},
{
"name": "reuse_size_classes",
"malloc": "//tcmalloc",
"deps": [
"//tcmalloc:common_8k_pages",
],
"env": {"TCMALLOC_REUSE_SIZE_CLASSES": "reuse"},
},
{
"name": "reuserelaxedbelow64_size_classes",
"malloc": "//tcmalloc",
"deps": [
"//tcmalloc:common_8k_pages",
],
"env": {"TCMALLOC_REUSE_SIZE_CLASSES": "reuserelaxedbelow64"},
},
{
"name": "hpaa",
"malloc": "//tcmalloc",
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