[PartitionAlloc] Remove thread cache purge feature, since it's enabled.

The feature has been enabled by default for a while, remove the code
corresponding to it, and clean up a function without any caller.

Bug: 998048
Change-Id: I006cc6ae81309dc0cbc2eaf74172e81374b9ebd5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3110605
Reviewed-by: Thiabaud Engelbrecht <thiabaud@google.com>
Commit-Queue: Benoit L <lizeb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#913812}

base/allocator/partition_allocator/extended_api.cc

@@ -10,7 +10,11 @@
 
 namespace base {
 
-namespace internal {
+#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC) && \
+    defined(PA_THREAD_CACHE_SUPPORTED)
+
+namespace {
+
 void DisableThreadCacheForRootIfEnabled(ThreadSafePartitionRoot* root) {
   // Some platforms don't have a thread cache, or it could already have been
   // disabled.
@@ -31,14 +35,27 @@ void EnablePartitionAllocThreadCacheForRootIfDisabled(
   root->with_thread_cache = true;
 }
 
-}  // namespace internal
+void DisablePartitionAllocThreadCacheForProcess() {
+  auto* regular_allocator = internal::PartitionAllocMalloc::Allocator();
+  auto* aligned_allocator = internal::PartitionAllocMalloc::AlignedAllocator();
+  DisableThreadCacheForRootIfEnabled(regular_allocator);
+  if (aligned_allocator != regular_allocator)
+    DisableThreadCacheForRootIfEnabled(aligned_allocator);
+  DisableThreadCacheForRootIfEnabled(
+      internal::PartitionAllocMalloc::OriginalAllocator());
+}
+
+}  // namespace
+
+#endif  // BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC) &&
+        // defined(PA_THREAD_CACHE_SUPPORTED)
 
 void SwapOutProcessThreadCacheForTesting(ThreadSafePartitionRoot* root) {
 #if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC) && \
     defined(PA_THREAD_CACHE_SUPPORTED)
   DisablePartitionAllocThreadCacheForProcess();
   internal::ThreadCache::SwapForTesting(root);
-  internal::EnablePartitionAllocThreadCacheForRootIfDisabled(root);
+  EnablePartitionAllocThreadCacheForRootIfDisabled(root);
 #endif  // BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC) &&
         // defined(PA_THREAD_CACHE_SUPPORTED)
 }
@@ -47,27 +64,14 @@ void SwapInProcessThreadCacheForTesting(ThreadSafePartitionRoot* root) {
 #if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC) && \
     defined(PA_THREAD_CACHE_SUPPORTED)
   // First, disable the test thread cache we have.
-  internal::DisableThreadCacheForRootIfEnabled(root);
+  DisableThreadCacheForRootIfEnabled(root);
 
-  auto* regular_allocator = base::internal::PartitionAllocMalloc::Allocator();
-  internal::EnablePartitionAllocThreadCacheForRootIfDisabled(regular_allocator);
+  auto* regular_allocator = internal::PartitionAllocMalloc::Allocator();
+  EnablePartitionAllocThreadCacheForRootIfDisabled(regular_allocator);
 
   internal::ThreadCache::SwapForTesting(regular_allocator);
 #endif  // BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC) &&
         // defined(PA_THREAD_CACHE_SUPPORTED)
 }
 
-void DisablePartitionAllocThreadCacheForProcess() {
-#if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
-  auto* regular_allocator = base::internal::PartitionAllocMalloc::Allocator();
-  auto* aligned_allocator =
-      base::internal::PartitionAllocMalloc::AlignedAllocator();
-  internal::DisableThreadCacheForRootIfEnabled(regular_allocator);
-  if (aligned_allocator != regular_allocator)
-    internal::DisableThreadCacheForRootIfEnabled(aligned_allocator);
-  internal::DisableThreadCacheForRootIfEnabled(
-      base::internal::PartitionAllocMalloc::OriginalAllocator());
-#endif  // BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
-}
-
 }  // namespace base

base/allocator/partition_allocator/extended_api.h

@@ -22,24 +22,6 @@ BASE_EXPORT void SwapOutProcessThreadCacheForTesting(
 BASE_EXPORT void SwapInProcessThreadCacheForTesting(
     ThreadSafePartitionRoot* root);
 
-// Disables the thread cache for the entire process.
-//
-// Saves memory but slows down the allocator *significantly*. Only use for
-// configurations that are very memory-constrained or performance-insensitive
-// processes.
-//
-// Must preferably be called from the main thread, when no/few threads have
-// been started.
-//
-// Otherwise, there are several things that can happen:
-// 1. Another thread is currently temporarily disabling the thread cache, and
-//    will re-enable it, negating this call's effect.
-// 2. Other threads' caches cannot be purged from here, and would retain their
-//    cached memory until thread destruction (where it is reclaimed).
-//
-// These are not correctness issues, at worst in the first case, memory is not
-// saved, and in the second one, *some* of the memory is leaked.
-BASE_EXPORT void DisablePartitionAllocThreadCacheForProcess();
 }  // namespace base
 
 #endif  // BASE_ALLOCATOR_PARTITION_ALLOCATOR_EXTENDED_API_H_

base/allocator/partition_allocator/partition_alloc_features.cc

@@ -26,10 +26,6 @@ const Feature kPartitionAllocPCScanBrowserOnly{
 const Feature kPartitionAllocBackupRefPtrControl{
     "PartitionAllocBackupRefPtrControl", FEATURE_DISABLED_BY_DEFAULT};
 
-// If enabled, the thread cache will be periodically purged.
-const Feature kPartitionAllocThreadCachePeriodicPurge{
-    "PartitionAllocThreadCachePeriodicPurge", FEATURE_ENABLED_BY_DEFAULT};
-
 // Use a larger maximum thread cache cacheable bucket size.
 const Feature kPartitionAllocLargeThreadCacheSize{
     "PartitionAllocLargeThreadCacheSize", FEATURE_DISABLED_BY_DEFAULT};

base/allocator/partition_allocator/partition_alloc_features.h

@@ -22,7 +22,6 @@ extern const BASE_EXPORT Feature kPartitionAllocPCScan;
 #if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
 extern const BASE_EXPORT Feature kPartitionAllocPCScanBrowserOnly;
 extern const BASE_EXPORT Feature kPartitionAllocBackupRefPtrControl;
-extern const BASE_EXPORT Feature kPartitionAllocThreadCachePeriodicPurge;
 extern const BASE_EXPORT Feature kPartitionAllocLargeThreadCacheSize;
 #endif  // BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
 

content/common/partition_alloc_support.cc

@@ -8,7 +8,6 @@
 
 #include "base/allocator/allocator_shim.h"
 #include "base/allocator/buildflags.h"
-#include "base/allocator/partition_allocator/extended_api.h"
 #include "base/allocator/partition_allocator/partition_alloc_config.h"
 #include "base/allocator/partition_allocator/partition_alloc_features.h"
 #include "base/allocator/partition_allocator/starscan/pcscan.h"
@@ -203,17 +202,6 @@ void PartitionAllocSupport::ReconfigureAfterFeatureListInit(
 
 #if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
   base::allocator::ReconfigurePartitionAllocLazyCommit();
-
-#if defined(OS_ANDROID)
-  // The thread cache consumes more memory. Don't use one on low-memory devices
-  // if thread cache purging is not enabled.
-  if (base::SysInfo::IsLowEndDevice() &&
-      !base::FeatureList::IsEnabled(
-          base::features::kPartitionAllocThreadCachePeriodicPurge)) {
-    base::DisablePartitionAllocThreadCacheForProcess();
-  }
-#endif  // defined(OS_ANDROID)
-
 #endif  // BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
 
   bool scan_enabled = EnablePCScanForMallocPartitionsIfNeeded();
@@ -263,20 +251,16 @@ void PartitionAllocSupport::ReconfigureAfterTaskRunnerInit(
   // initialized later.
   DCHECK(process_type != switches::kZygoteProcess);
 
-  if (base::FeatureList::IsEnabled(
-          base::features::kPartitionAllocThreadCachePeriodicPurge)) {
-    auto& registry = base::internal::ThreadCacheRegistry::Instance();
-    registry.StartPeriodicPurge();
+  auto& registry = base::internal::ThreadCacheRegistry::Instance();
+  registry.StartPeriodicPurge();
 
 #if defined(OS_ANDROID)
-    // Lower thread cache limits to avoid stranding too much memory in the
-    // caches.
-    if (base::SysInfo::IsLowEndDevice()) {
-      registry.SetThreadCacheMultiplier(
-          base::internal::ThreadCache::kDefaultMultiplier / 2.);
-    }
-#endif  // defined(OS_ANDROID)
+  // Lower thread cache limits to avoid stranding too much memory in the caches.
+  if (base::SysInfo::IsLowEndDevice()) {
+    registry.SetThreadCacheMultiplier(
+        base::internal::ThreadCache::kDefaultMultiplier / 2.);
   }
+#endif  // defined(OS_ANDROID)
 
   // Renderer processes are more performance-sensitive, increase thread cache
   // limits.