PartitionDumpStats(): reduce stack consumption for 'light' reporting.

base/allocator/partition_allocator/partition_alloc.cc

Index: base/allocator/partition_allocator/partition_alloc.cc
diff --git a/base/allocator/partition_allocator/partition_alloc.cc b/base/allocator/partition_allocator/partition_alloc.cc
index 37d2633b95d59d298c1bf2f538dbe7a7c888c009..439ce177d88a5061ce42e50b50b94f8f0a923a1e 100644
--- a/base/allocator/partition_allocator/partition_alloc.cc
+++ b/base/allocator/partition_allocator/partition_alloc.cc
@@ -1396,27 +1396,42 @@ void PartitionDumpStats(PartitionRoot* partition,
                         const char* partition_name,
                         bool is_light_dump,
                         PartitionStatsDumper* dumper) {
-  static const size_t kMaxReportableBuckets = 4096 / sizeof(void*);
-  PartitionBucketMemoryStats memory_stats[kMaxReportableBuckets];
-  const size_t partitionNumBuckets = partition->num_buckets;
-  DCHECK(partitionNumBuckets <= kMaxReportableBuckets);
-
-  for (size_t i = 0; i < partitionNumBuckets; ++i)
-    PartitionDumpBucketStats(&memory_stats[i], &partition->buckets()[i]);
 
-  // PartitionsDumpBucketStats is called after collecting stats because it
-  // can use PartitionAlloc to allocate and this can affect the statistics.
   PartitionMemoryStats stats = {0};
   stats.total_mmapped_bytes = partition->total_size_of_super_pages;
   stats.total_committed_bytes = partition->total_size_of_committed_pages;
   DCHECK(!partition->total_size_of_direct_mapped_pages);
+
+  static const size_t kMaxReportableBuckets = 4096 / sizeof(void*);
+  std::unique_ptr<PartitionBucketMemoryStats[]> memory_stats;
+  if (!is_light_dump)
+    memory_stats = std::unique_ptr<PartitionBucketMemoryStats[]>(
+        new PartitionBucketMemoryStats[kMaxReportableBuckets]);
+
+  const size_t partitionNumBuckets = partition->num_buckets;
+  DCHECK(partitionNumBuckets <= kMaxReportableBuckets);
+
   for (size_t i = 0; i < partitionNumBuckets; ++i) {
-    if (memory_stats[i].is_valid) {
-      stats.total_resident_bytes += memory_stats[i].resident_bytes;
-      stats.total_active_bytes += memory_stats[i].active_bytes;
-      stats.total_decommittable_bytes += memory_stats[i].decommittable_bytes;
-      stats.total_discardable_bytes += memory_stats[i].discardable_bytes;
-      if (!is_light_dump)
+    PartitionBucketMemoryStats bucket_stats = {0};
+    PartitionDumpBucketStats(&bucket_stats, &partition->buckets()[i]);
+    if (bucket_stats.is_valid) {
+      stats.total_resident_bytes += bucket_stats.resident_bytes;
+      stats.total_active_bytes += bucket_stats.active_bytes;
+      stats.total_decommittable_bytes += bucket_stats.decommittable_bytes;
+      stats.total_discardable_bytes += bucket_stats.discardable_bytes;
+    }
+    if (!is_light_dump) {
+      if (bucket_stats.is_valid)
+        memory_stats[i] = bucket_stats;
+      else
+        memory_stats[i].is_valid = false;
+    }
+  }
+  if (!is_light_dump) {
+    // PartitionsDumpBucketStats is called after collecting stats because it
+    // can use PartitionAlloc to allocate and this can affect the statistics.
+    for (size_t i = 0; i < partitionNumBuckets; ++i) {
+      if (memory_stats[i].is_valid)
         dumper->PartitionsDumpBucketStats(partition_name, &memory_stats[i]);
     }
   }