From 653e7cdd94986aeec8db3bfb07e49d029c980898 Mon Sep 17 00:00:00 2001
From: TCMalloc Team <tcmalloc-eng@google.com>
Date: Wed, 7 Oct 2026 09:12:02 -0700
Subject: [PATCH] Batch LinkedSample deletion under metadata_lock_ in
 ~StackTraceTable

Add a callback-based batch overload to MetadataObjectAllocator::Delete(absl::FunctionRef<T* absl_nullable()> callback) and use it in StackTraceTable::~StackTraceTable() so the singly-linked list of LinkedSample nodes is drained under a single metadata_lock_ acquisition instead of bouncing the lock on every node.

PiperOrigin-RevId: 995150983
---
 tcmalloc/metadata_object_allocator.h | 10 ++++++++++
 tcmalloc/stack_trace_table.cc        | 13 +++++++++----
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/tcmalloc/metadata_object_allocator.h b/tcmalloc/metadata_object_allocator.h
index 9b7f982db..cfd394cc1 100644
--- a/tcmalloc/metadata_object_allocator.h
+++ b/tcmalloc/metadata_object_allocator.h
@@ -23,8 +23,10 @@
 #include "absl/base/const_init.h"
 #include "absl/base/dynamic_annotations.h"
 #include "absl/base/internal/spinlock.h"
+#include "absl/base/nullability.h"
 #include "absl/base/optimization.h"
 #include "absl/base/thread_annotations.h"
+#include "absl/functional/function_ref.h"
 #include "absl/types/span.h"
 #include "tcmalloc/arena.h"
 #include "tcmalloc/common.h"
@@ -88,6 +90,14 @@ class MetadataObjectAllocator {
     }
   }
 
+  void Delete(absl::FunctionRef<T* absl_nullable()> callback) {
+    AllocationGuardSpinLockHolder l(metadata_lock_);
+    while (T* p = callback()) {
+      p->~T();
+      DeleteMemory(p);
+    }
+  }
+
   [[nodiscard]] AllocatorStats stats() const {
     AllocationGuardSpinLockHolder l(metadata_lock_);
 
diff --git a/tcmalloc/stack_trace_table.cc b/tcmalloc/stack_trace_table.cc
index 6afbfcf0f..d96ec66f2 100644
--- a/tcmalloc/stack_trace_table.cc
+++ b/tcmalloc/stack_trace_table.cc
@@ -40,11 +40,16 @@ StackTraceTable::StackTraceTable(ProfileType type)
 
 StackTraceTable::~StackTraceTable() {
   LinkedSample* cur = all_;
-  while (cur != nullptr) {
-    LinkedSample* next = cur->next;
-    tc_globals.linked_sample_allocator().Delete(cur);
-    cur = next;
+  if (cur == nullptr) {
+    return;
   }
+  tc_globals.linked_sample_allocator().Delete([&]() -> LinkedSample* {
+    LinkedSample* s = cur;
+    if (s != nullptr) {
+      cur = s->next;
+    }
+    return s;
+  });
   all_ = nullptr;
 }