base: Add a trace counter for amount of discardable memory allocated.

This adds a trace counter to the discardable memory manager for
the amount of memory allocated. Useful when debugging performance
issues related to discardable memory usage.

BUG=310231

Review URL: https://codereview.chromium.org/234363002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@263221 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 16 insertions, 0 deletions

diff --git a/base/memory/discardable_memory_manager.cc b/base/memory/discardable_memory_manager.cc
index c1b9f36..e31f932 100644
--- a/base/memory/discardable_memory_manager.cc
+++ b/base/memory/discardable_memory_manager.cc
@@ -30,6 +30,7 @@ DiscardableMemoryManager::DiscardableMemoryManager()
       discardable_memory_limit_(kDefaultDiscardableMemoryLimit),
       bytes_to_keep_under_moderate_pressure_(
           kDefaultBytesToKeepUnderModeratePressure) {
+  BytesAllocatedChanged();
 }
 
 DiscardableMemoryManager::~DiscardableMemoryManager() {
@@ -88,6 +89,7 @@ void DiscardableMemoryManager::Unregister(
     size_t bytes = it->second.bytes;
     DCHECK_LE(bytes, bytes_allocated_);
     bytes_allocated_ -= bytes;
+    BytesAllocatedChanged();
     free(it->second.memory);
   }
   allocations_.Erase(it);
@@ -130,6 +132,8 @@ scoped_ptr<uint8, FreeDeleter> DiscardableMemoryManager::Acquire(
     return scoped_ptr<uint8, FreeDeleter>();
 
   bytes_allocated_ += bytes;
+  BytesAllocatedChanged();
+
   *purged = true;
   return memory.Pass();
 }
@@ -217,11 +221,20 @@ void DiscardableMemoryManager::PurgeLRUWithLockAcquiredUntilUsageIsWithin(
     free(it->second.memory);
     it->second.memory = NULL;
   }
+
+  BytesAllocatedChanged();
 }
 
 void DiscardableMemoryManager::EnforcePolicyWithLockAcquired() {
   PurgeLRUWithLockAcquiredUntilUsageIsWithin(discardable_memory_limit_);
 }
 
+void DiscardableMemoryManager::BytesAllocatedChanged() const {
+  TRACE_COUNTER_ID1("base",
+                    "DiscardableMemoryUsage",
+                    this,
+                    bytes_allocated_);
+}
+
 }  // namespace internal
 }  // namespace base
diff --git a/base/memory/discardable_memory_manager.h b/base/memory/discardable_memory_manager.h
index 2b72c51..7c0bd5c 100644
--- a/base/memory/discardable_memory_manager.h
+++ b/base/memory/discardable_memory_manager.h
@@ -121,6 +121,9 @@ class BASE_EXPORT_PRIVATE DiscardableMemoryManager {
   // Caller must acquire |lock_| prior to calling this function.
   void EnforcePolicyWithLockAcquired();
 
+  // Called when a change to |bytes_allocated_| has been made.
+  void BytesAllocatedChanged() const;
+
   // Needs to be held when accessing members.
   mutable Lock lock_;