Clean up experiment for hugepaging tcmalloc metadata.

PiperOrigin-RevId: 684573208
Change-Id: I17b9c5e332b4ac63ae532e680259fffa95d3e2cb

tcmalloc/experiment_config.h

@@ -24,7 +24,6 @@ enum class Experiment : int {
   // clang-format off
   TEST_ONLY_TCMALLOC_POW2_SIZECLASS,
   TEST_ONLY_TCMALLOC_SHARDED_TRANSFER_CACHE,
-  TCMALLOC_METADATA_HUGEPAGE,  // TODO(b/345239704): Complete experiment.
   TEST_ONLY_TCMALLOC_HUGE_CACHE_RELEASE_30S,  // TODO(b/319872040): Complete experiment.
   TEST_ONLY_TCMALLOC_REUSE_SIZE_CLASSES,  // TODO(b/358126781): Complete experiment.
   TCMALLOC_HUGE_REGION_DEMAND_BASED_RELEASE,  // TODO(b/328440160): Complete experiment.
@@ -45,7 +44,6 @@ struct ExperimentConfig {
 inline constexpr ExperimentConfig experiments[] = {
     {Experiment::TEST_ONLY_TCMALLOC_POW2_SIZECLASS, "TEST_ONLY_TCMALLOC_POW2_SIZECLASS"},
     {Experiment::TEST_ONLY_TCMALLOC_SHARDED_TRANSFER_CACHE, "TEST_ONLY_TCMALLOC_SHARDED_TRANSFER_CACHE"},
-    {Experiment::TCMALLOC_METADATA_HUGEPAGE, "TCMALLOC_METADATA_HUGEPAGE"},
     {Experiment::TEST_ONLY_TCMALLOC_HUGE_CACHE_RELEASE_30S, "TEST_ONLY_TCMALLOC_HUGE_CACHE_RELEASE_30S"},
     {Experiment::TEST_ONLY_TCMALLOC_REUSE_SIZE_CLASSES, "TEST_ONLY_TCMALLOC_REUSE_SIZE_CLASSES"},
     {Experiment::TCMALLOC_HUGE_REGION_DEMAND_BASED_RELEASE, "TCMALLOC_HUGE_REGION_DEMAND_BASED_RELEASE"},

tcmalloc/parameters.cc

@@ -121,19 +121,6 @@ static std::atomic<bool>& huge_region_demand_based_release_enabled() {
   return v;
 }
 
-// As set_metadata_hugepage is determined at runtime, we cannot require constant
-// initialization for the atomic.  This avoids an initialization order fiasco.
-static std::atomic<bool>& tag_metadata_hugepage_enabled() {
-  ABSL_CONST_INIT static absl::once_flag flag;
-  ABSL_CONST_INIT static std::atomic<bool> v{true};
-  absl::base_internal::LowLevelCallOnce(&flag, [&]() {
-    if (IsExperimentActive(Experiment::TCMALLOC_METADATA_HUGEPAGE)) {
-      v.store(false, std::memory_order_relaxed);
-    }
-  });
-  return v;
-}
-
 // Configures short and long intervals to zero by default. We expect to set them
 // to the non-zero durations once the feature is no longer experimental.
 static std::atomic<int64_t>& skip_subrelease_short_interval_ns() {
@@ -284,7 +271,6 @@ ABSL_CONST_INIT std::atomic<bool> Parameters::per_cpu_caches_dynamic_slab_(
     true);
 ABSL_CONST_INIT std::atomic<MadvisePreference> Parameters::madvise_(
     MadvisePreference::kDontNeed);
-ABSL_CONST_INIT std::atomic<bool> Parameters::tag_metadata_separately_(true);
 ABSL_CONST_INIT std::atomic<tcmalloc::hot_cold_t>
     Parameters::min_hot_access_hint_(kDefaultMinHotAccessHint);
 ABSL_CONST_INIT std::atomic<double>
@@ -339,10 +325,6 @@ bool Parameters::huge_region_demand_based_release() {
       std::memory_order_relaxed);
 }
 
-bool Parameters::tag_metadata_separately() {
-  return tag_metadata_hugepage_enabled().load(std::memory_order_relaxed);
-}
-
 bool Parameters::dense_trackers_sorted_on_spans_allocated() {
   ABSL_CONST_INIT static absl::once_flag flag;
   ABSL_CONST_INIT static std::atomic<bool> v{false};
@@ -510,10 +492,6 @@ bool TCMalloc_Internal_GetReleasePagesFromHugeRegionEnabled() {
   return Parameters::release_pages_from_huge_region();
 }
 
-bool TCMalloc_Internal_GetTagMetadataSeparatelyEnabled() {
-  return Parameters::tag_metadata_separately();
-}
-
 bool TCMalloc_Internal_GetResizeSizeClassMaxCapacityEnabled() {
   return Parameters::resize_size_class_max_capacity();
 }
@@ -583,11 +561,6 @@ void TCMalloc_Internal_SetReleasePagesFromHugeRegionEnabled(bool v) {
                                                     std::memory_order_relaxed);
 }
 
-void TCMalloc_Internal_SetTagMetadataSeparatelyEnabled(bool v) {
-  tcmalloc::tcmalloc_internal::tag_metadata_hugepage_enabled().store(
-      v, std::memory_order_relaxed);
-}
-
 void TCMalloc_Internal_SetResizeSizeClassMaxCapacityEnabled(bool v) {
   Parameters::resize_size_class_max_capacity_.store(v,
                                                     std::memory_order_relaxed);

tcmalloc/parameters.h

@@ -114,12 +114,6 @@ class Parameters {
     return release_pages_from_huge_region_.load(std::memory_order_relaxed);
   }
 
-  static bool tag_metadata_separately();
-
-  static void set_tag_metadata_separately(bool value) {
-    TCMalloc_Internal_SetTagMetadataSeparatelyEnabled(value);
-  }
-
   static bool resize_size_class_max_capacity() {
     return resize_size_class_max_capacity_.load(std::memory_order_relaxed);
   }
@@ -230,7 +224,6 @@ class Parameters {
   friend void ::TCMalloc_Internal_SetHugeCacheDemandBasedRelease(bool v);
   friend void ::TCMalloc_Internal_SetHugeRegionDemandBasedRelease(bool v);
   friend void ::TCMalloc_Internal_SetReleasePagesFromHugeRegionEnabled(bool v);
-  friend void ::TCMalloc_Internal_SetTagMetadataSeparatelyEnabled(bool v);
   friend void ::TCMalloc_Internal_SetResizeSizeClassMaxCapacityEnabled(bool v);
   friend void ::TCMalloc_Internal_SetMaxPerCpuCacheSize(int32_t v);
   friend void ::TCMalloc_Internal_SetMaxTotalThreadCacheBytes(int64_t v);
@@ -272,7 +265,6 @@ class Parameters {
   static std::atomic<bool> huge_cache_demand_based_release_;
   static std::atomic<bool> release_pages_from_huge_region_;
   static std::atomic<bool> resize_size_class_max_capacity_;
-  static std::atomic<bool> tag_metadata_separately_;
   static std::atomic<int64_t> profile_sampling_interval_;
   static std::atomic<bool> per_cpu_caches_dynamic_slab_;
   static std::atomic<MadvisePreference> madvise_;

tcmalloc/system-alloc.cc

@@ -288,10 +288,7 @@ static AddressRegionFactory::UsageHint TagToHint(MemoryTag tag) {
     case MemoryTag::kCold:
       return UsageHint::kInfrequentAccess;
     case MemoryTag::kMetadata:
-      if (Parameters::tag_metadata_separately()) {
-        return UsageHint::kMetadata;
-      }
-      return UsageHint::kInfrequentAllocation;
+      return UsageHint::kMetadata;
   }
 
   ASSUME(false);

tcmalloc/testing/system-alloc_test.cc

@@ -32,7 +32,6 @@
 #include "tcmalloc/internal/logging.h"
 #include "tcmalloc/internal/proc_maps.h"
 #include "tcmalloc/malloc_extension.h"
-#include "tcmalloc/parameters.h"
 
 #ifndef PR_SET_VMA
 #define PR_SET_VMA 0x53564d41
@@ -224,9 +223,8 @@ TEST(Basic, RetryFailTest) {
   free(q);
 }
 
-// Verify when tag_metadata_separately is true, the usage hint is kMetadata.
+// Verify default behavior for tcmalloc metadata utilizes usage hint kMetadata.
 TEST(UsageHint, VerifyUsageHintkMetadataTest) {
-  Parameters::set_tag_metadata_separately(true);
   MallocExtension::SetRegionFactory(&f);
   // Need a large enough size to trigger the system allocator,
   //  2.0 is an arbitrary number. Else it would continue to use the previous
@@ -238,21 +236,6 @@ TEST(UsageHint, VerifyUsageHintkMetadataTest) {
   ::operator delete(ptr);
 }
 
-// Verify that when tag_metadata_separately is false, the usage hint is
-// kInfrequentAllocation.
-TEST(UsageHint, WhenNotTaggingMetadataSeparately) {
-  Parameters::set_tag_metadata_separately(false);
-  MallocExtension::SetRegionFactory(&f);
-  // Need a large enough size to trigger the system allocator,
-  //  2.0 is an arbitrary number. Else it would continue to use the previous
-  //  hugepage region and a new usage hint wouldn't be assigned
-  void* ptr = ::operator new(kMinMmapAlloc * 2.0);
-  EXPECT_EQ(f.usage_hint_,
-            AddressRegionFactory::UsageHint::kInfrequentAllocation)
-      << "Usage hint is " << hintToString(f.usage_hint_);
-  ::operator delete(ptr);
-}
-
 }  // namespace
 }  // namespace tcmalloc_internal
 }  // namespace tcmalloc