From 490ee515a66b15dfcaa096c6f42ae5d97fa907ca Mon Sep 17 00:00:00 2001
From: Vaibhav Gogte CA <vgogte@google.com>
Date: Wed, 23 Sep 2026 15:16:00 -0700
Subject: [PATCH] Shrink sizes of per-size-class misses and overall cache
 misses from std::atomic<size_t> down to std::atomic<uint32_t>. Since
 differences are computed with unsigned arithmetic wrapping and returned as
 size_t or handled correctly in comparisons, wrap around behaviors evaluate
 correctly and perfectly safe.

PiperOrigin-RevId: 987036273
---
 tcmalloc/cpu_cache.h | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tcmalloc/cpu_cache.h b/tcmalloc/cpu_cache.h
index 1a34c2dc5..de1ee04d7 100644
--- a/tcmalloc/cpu_cache.h
+++ b/tcmalloc/cpu_cache.h
@@ -528,10 +528,10 @@ class CpuCache {
   using Freelist = subtle::percpu::TcmallocSlab<kNumClasses>;
 
   struct PerClassMissCounts {
-    std::atomic<size_t>
+    std::atomic<uint32_t>
         misses[static_cast<size_t>(PerClassMissType::kNumTypes)];
 
-    std::atomic<size_t>& operator[](PerClassMissType type) {
+    std::atomic<uint32_t>& operator[](PerClassMissType type) {
       return misses[static_cast<size_t>(type)];
     }
   };
@@ -588,9 +588,9 @@ class CpuCache {
 
   // Helper type so we don't need to sprinkle `static_cast`s everywhere.
   struct MissCounts {
-    std::atomic<size_t> misses[static_cast<size_t>(MissCount::kNumCounts)];
+    std::atomic<uint32_t> misses[static_cast<size_t>(MissCount::kNumCounts)];
 
-    std::atomic<size_t>& operator[](MissCount miss_count) {
+    std::atomic<uint32_t>& operator[](MissCount miss_count) {
       return misses[static_cast<size_t>(miss_count)];
     }
   };