Align base::Pickle allocations to 4k boundaries

base/trace_event/trace_event_argument.cc

 // Copyright (c) 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/trace_event/trace_event_argument.h"
 
+#include "base/bits.h"
 #include "base/json/json_writer.h"
 #include "base/trace_event/trace_event_memory_overhead.h"
 #include "base/values.h"
 
 namespace base {
 namespace trace_event {
 
 namespace {
 const char kTypeStartDict = '{';
 const char kTypeEndDict = '}';
@@ skipping 429 matching lines @@
   // TODO(primiano): this could be smarter, skip the ToBaseValue encoding and
   // produce the JSON on its own. This will require refactoring JSONWriter
   // to decouple the base::Value traversal from the JSON writing bits
   std::string tmp;
   JSONWriter::Write(*ToBaseValue(), &tmp);
   *out += tmp;
 }
 
 void TracedValue::EstimateTraceMemoryOverhead(
     TraceEventMemoryOverhead* overhead) {
+  const size_t kPickleAlignment = 4096;

[Lei Zhang, 2015/07/24 01:36:48]

Is this assuming |kPickleHeapAlign| in pickle.cc is 4096?

[Primiano Tucci (use gerrit), 2015/07/24 09:37:38]

Yes. It felt a bit of a stretch exposing it as a public const of base::Pickle as
it is an implementation detail and I find hard to think about other cases where
you need to know the heap size of Pickle. WDYT?
Should I move it to be Pickle::kPickleHeapAlign ?

I changed the name here (to match kPickleHeapAlign) and added a comment

[Lei Zhang, 2015/07/24 18:59:55]

Ok. Maybe expose it if we ever find another need to expose it.

   overhead->Add("TracedValue",
-                pickle_.GetTotalAllocatedSize() /* allocated size */,
-                pickle_.size() /* resident size */);
+
+                /* allocated size */
+                bits::Align(pickle_.GetTotalAllocatedSize(), kPickleAlignment),
+
+                /* resident size */
+                bits::Align(pickle_.size(), kPickleAlignment));
 }
 
 }  // namespace trace_event
 }  // namespace base