[GC] Increase heap max_global_memory_size

etiennep-chromium · V8 LUCI CQ · commit 33a3d373f910 · 2025-09-09T13:13:09.000-07:00
Under external_memory_accounted_in_global_limit, external memory counts towards GlobalConsumedBytes(), which makes it more likely to reach max_global_memory_size. When this happens, allocation limits don't make a lot of sense, so this pushes back max_global_memory_size by a factor of 4, capped by `physical_memory`. Meanwhile, I'm also making another check more strict which will lead to an OOM if we still reach max_global_memory_size https://chromium-review.googlesource.com/c/v8/v8/+/6931616 Bug: 361124432 Change-Id: I3f3f940249da0579b86c2c2286e090bf09c0021a Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/6931611 Reviewed-by: Michael Lippautz <mlippautz@chromium.org> Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org> Cr-Commit-Position: refs/heads/main@{#102367}
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
@@ -1479,11 +1479,15 @@ size_t GlobalMemorySizeFromV8Size(size_t v8_size) {
 
 }  // anonymous namespace
 
-void Heap::SetOldGenerationAndGlobalMaximumSize(
-    size_t max_old_generation_size) {
+void Heap::SetOldGenerationAndGlobalMaximumSize(size_t max_old_generation_size,
+                                                size_t physical_memory) {
   max_old_generation_size_.store(max_old_generation_size,
                                  std::memory_order_relaxed);
-  max_global_memory_size_ = GlobalMemorySizeFromV8Size(max_old_generation_size);
+  max_global_memory_size_ =
+      v8_flags.external_memory_accounted_in_global_limit
+          ? std::min(physical_memory,
+                     4 * GlobalMemorySizeFromV8Size(max_old_generation_size))
+          : GlobalMemorySizeFromV8Size(max_old_generation_size);
 }
 
 void Heap::SetOldGenerationAndGlobalAllocationLimit(
@@ -1673,7 +1677,8 @@ void Heap::CollectGarbage(AllocationSpace space,
       if (initial_max_old_generation_size_ < max_old_generation_size() &&
           OldGenerationSizeOfObjects() <
               initial_max_old_generation_size_threshold_) {
-        SetOldGenerationAndGlobalMaximumSize(initial_max_old_generation_size_);
+        SetOldGenerationAndGlobalMaximumSize(initial_max_old_generation_size_,
+                                             physical_memory());
       }
     }
 
@@ -2584,8 +2589,6 @@ void Heap::RecomputeLimits(GarbageCollector collector, base::TimeTicks time) {
         new_old_generation_allocation_limit, new_global_allocation_limit);
   }
 
-  CHECK_EQ(max_global_memory_size_,
-           GlobalMemorySizeFromV8Size(max_old_generation_size_));
   CHECK_GE(global_allocation_limit(), old_generation_allocation_limit_);
 }
 
@@ -2632,8 +2635,6 @@ void Heap::RecomputeLimitsAfterLoadingIfNeeded() {
   SetOldGenerationAndGlobalAllocationLimit(new_old_generation_allocation_limit,
                                            new_global_allocation_limit);
 
-  CHECK_EQ(max_global_memory_size_,
-           GlobalMemorySizeFromV8Size(max_old_generation_size_));
   CHECK_GE(global_allocation_limit(), old_generation_allocation_limit_);
 }
 
@@ -4354,8 +4355,10 @@ bool Heap::InvokeNearHeapLimitCallback() {
     size_t heap_limit = callback(data, max_old_generation_size(),
                                  initial_max_old_generation_size_);
     if (heap_limit > max_old_generation_size()) {
-      SetOldGenerationAndGlobalMaximumSize(std::min(
-          heap_limit, AllocatorLimitOnMaxOldGenerationSize(physical_memory())));
+      SetOldGenerationAndGlobalMaximumSize(
+          std::min(heap_limit,
+                   AllocatorLimitOnMaxOldGenerationSize(physical_memory())),
+          physical_memory());
       return true;
     }
   }
@@ -5171,7 +5174,8 @@ void Heap::ConfigureHeap(const v8::ResourceConstraints& constraints,
     max_old_generation_size =
         RoundDown<PageMetadata::kPageSize>(max_old_generation_size);
 
-    SetOldGenerationAndGlobalMaximumSize(max_old_generation_size);
+    SetOldGenerationAndGlobalMaximumSize(
+        max_old_generation_size, constraints.physical_memory_size_in_bytes());
   }
 
   CHECK_IMPLIES(
diff --git a/src/heap/heap.h b/src/heap/heap.h
@@ -711,7 +711,8 @@ class Heap final {
     // Do not set the limit lower than the live size + some slack.
     size_t min_limit = SizeOfObjects() + SizeOfObjects() / 4;
     SetOldGenerationAndGlobalMaximumSize(
-        std::min(max_old_generation_size(), std::max(heap_limit, min_limit)));
+        std::min(max_old_generation_size(), std::max(heap_limit, min_limit)),
+        physical_memory());
   }
 
   // ===========================================================================
@@ -2019,7 +2020,8 @@ class Heap final {
 
   // Sets max_old_generation_size_ and computes the new global heap limit from
   // it.
-  void SetOldGenerationAndGlobalMaximumSize(size_t max_old_generation_size);
+  void SetOldGenerationAndGlobalMaximumSize(size_t max_old_generation_size,
+                                            size_t physical_memory);
 
   // Sets allocation limits for both old generation and the global heap.
   void SetOldGenerationAndGlobalAllocationLimit(
