Increase number of bits for trace buffer chunk index

The buffer for "record-as-much-as-possible" mode contains too many
chunks whose chunk indices to be contained in the 16 bit chunk index.

Increase chunk index to 26 bits.

BUG=516056
R=brianderson@chromium.org
TBR=dsinclair@chromium.org,nduca@chromium.org
TEST=Compile time static_asserts

Review URL: https://codereview.chromium.org/1276163003

Cr-Commit-Position: refs/heads/master@{#342495}

3 files changed, 19 insertions, 4 deletions

diff --git a/base/trace_event/trace_buffer.h b/base/trace_event/trace_buffer.h
index 4074120..d54bd74 100644
--- a/base/trace_event/trace_buffer.h
+++ b/base/trace_event/trace_buffer.h
@@ -40,6 +40,10 @@ class BASE_EXPORT TraceBufferChunk {
 
   void EstimateTraceMemoryOverhead(TraceEventMemoryOverhead* overhead);
 
+  // These values must be kept consistent with the numbers of bits of
+  // chunk_index and event_index fields in TraceEventHandle
+  // (in trace_event_impl.h).
+  static const size_t kMaxChunkIndex = (1u << 26) - 1;
   static const size_t kTraceBufferChunkSize = 64;
 
  private:
diff --git a/base/trace_event/trace_event_impl.h b/base/trace_event/trace_event_impl.h
index 8e9b3b0..0d66bb2 100644
--- a/base/trace_event/trace_event_impl.h
+++ b/base/trace_event/trace_event_impl.h
@@ -66,8 +66,11 @@ const int kTraceMaxNumArgs = 2;
 
 struct TraceEventHandle {
   uint32 chunk_seq;
-  uint16 chunk_index;
-  uint16 event_index;
+  // These numbers of bits must be kept consistent with
+  // TraceBufferChunk::kMaxTrunkIndex and
+  // TraceBufferChunk::kTraceBufferChunkSize (in trace_buffer.h).
+  unsigned chunk_index : 26;
+  unsigned event_index : 6;
 };
 
 class BASE_EXPORT TraceEvent {
diff --git a/base/trace_event/trace_log.cc b/base/trace_event/trace_log.cc
index 56c01c1..8eb46c5 100644
--- a/base/trace_event/trace_log.cc
+++ b/base/trace_event/trace_log.cc
@@ -58,10 +58,18 @@ namespace {
 // Controls the number of trace events we will buffer in-memory
 // before throwing them away.
 const size_t kTraceBufferChunkSize = TraceBufferChunk::kTraceBufferChunkSize;
+
 const size_t kTraceEventVectorBigBufferChunks =
     512000000 / kTraceBufferChunkSize;
+static_assert(
+    kTraceEventVectorBigBufferChunks <= TraceBufferChunk::kMaxChunkIndex,
+    "Too many big buffer chunks");
 const size_t kTraceEventVectorBufferChunks = 256000 / kTraceBufferChunkSize;
+static_assert(
+    kTraceEventVectorBufferChunks <= TraceBufferChunk::kMaxChunkIndex,
+    "Too many vector buffer chunks");
 const size_t kTraceEventRingBufferChunks = kTraceEventVectorBufferChunks / 4;
+
 // Can store results for 30 seconds with 1 ms sampling interval.
 const size_t kMonitorTraceEventBufferChunks = 30000 / kTraceBufferChunkSize;
 // ECHO_TO_CONSOLE needs a small buffer to hold the unfinished COMPLETE events.
@@ -167,8 +175,8 @@ void MakeHandle(uint32 chunk_seq,
                 size_t event_index,
                 TraceEventHandle* handle) {
   DCHECK(chunk_seq);
-  DCHECK(chunk_index < (1u << 16));
-  DCHECK(event_index < (1u << 16));
+  DCHECK(chunk_index <= TraceBufferChunk::kMaxChunkIndex);
+  DCHECK(event_index < TraceBufferChunk::kTraceBufferChunkSize);
   handle->chunk_seq = chunk_seq;
   handle->chunk_index = static_cast<uint16>(chunk_index);
   handle->event_index = static_cast<uint16>(event_index);