[DOMStorage] Rate limiting writes to disk.

content/browser/dom_storage/dom_storage_area.h

Index: content/browser/dom_storage/dom_storage_area.h
diff --git a/content/browser/dom_storage/dom_storage_area.h b/content/browser/dom_storage/dom_storage_area.h
index ca28be1aa144da7a55a984a3fdf2f1cdc96d50ed..53a7217893eac1a01c5ef86136da2d9cacea7e34 100644
--- a/content/browser/dom_storage/dom_storage_area.h
+++ b/content/browser/dom_storage/dom_storage_area.h
@@ -95,11 +95,47 @@ class CONTENT_EXPORT DOMStorageArea
   FRIEND_TEST_ALL_PREFIXES(DOMStorageContextImplTest, PersistentIds);
   friend class base::RefCountedThreadSafe<DOMStorageArea>;
 
+  class RateLimiter {

[cmumford, 2015/02/03 00:45:24]

Why not put the implementation of RateLimiter in the *.cc file? I'm not sure
what the rule here is.

[michaeln, 2015/02/03 19:59:15]

because i wasn't done yet :)

+   public:
+    RateLimiter(size_t desired_rate, base::TimeDelta time_quantum)
+        : rate_(desired_rate),
+          samples_(0),
+          time_quantum_(time_quantum) {
+    DCHECK(desired_rate > 0);

[cmumford, 2015/02/03 00:45:24]

Consider using DCHECK_GT instead of DCHECK(a > b)

[michaeln, 2015/02/03 19:59:15]

Done.

+  }

[cmumford, 2015/02/03 00:45:24]

Indenting looks wrong - Reitveld issue?

+
+    void AddSamples(size_t samples) { samples_ += samples; }
+
+    // Computes the total time needed to process the total samples seen
+    // at the desired rate.
+    base::TimeDelta ComputeTimeNeeded() {

[cmumford, 2015/02/03 00:45:24]

Should this be const?

[michaeln, 2015/02/03 19:59:14]

Done.

+      return base::TimeDelta::FromInternalValue
+          ((samples_ / rate_) * time_quantum_.ToInternalValue());
+    }
+
+    // Given the elapsed time since the start of the rate limiting session,
+    // computes the delay needed to mimic having processed the total samples
+    // seen at the desired rate.
+    base::TimeDelta ComputeDelayNeeded(const base::TimeDelta elapsed_time) {

[cmumford, 2015/02/03 00:45:24]

Should be a static method?

[michaeln, 2015/02/03 19:59:15]

can't be, this uses the instance method ComputeTimeNeeded()

[cmumford, 2015/02/04 18:43:54]

Then it can be const right?

+      base::TimeDelta time_needed = ComputeTimeNeeded();
+      if (time_needed > elapsed_time)
+        return time_needed - elapsed_time;
+      return base::TimeDelta();
+    }
+
+   private:
+    double rate_;
+    double samples_;
+    base::TimeDelta time_quantum_;
+  };
+
   struct CommitBatch {
     bool clear_all_first;
     DOMStorageValuesMap changed_values;
+
     CommitBatch();
     ~CommitBatch();
+    size_t GetDataSize();

[cmumford, 2015/02/03 00:45:24]

const method.

[michaeln, 2015/02/03 19:59:14]

Done.

   };
 
   ~DOMStorageArea();
@@ -116,6 +152,7 @@ class CONTENT_EXPORT DOMStorageArea
   void OnCommitTimer();
   void CommitChanges(const CommitBatch* commit_batch);
   void OnCommitComplete();
+  base::TimeDelta ComputeCommitDelay();

[cmumford, 2015/02/03 00:45:24]

const

[michaeln, 2015/02/03 19:59:14]

Done.

 
   void ShutdownInCommitSequence();
 
@@ -131,6 +168,9 @@ class CONTENT_EXPORT DOMStorageArea
   bool is_shutdown_;
   scoped_ptr<CommitBatch> commit_batch_;
   int commit_batches_in_flight_;
+  base::Time start_time_;
+  RateLimiter data_rate_limiter_;
+  RateLimiter commit_rate_limiter_;
 };
 
 }  // namespace content