gpu: Reuse transfer buffers more aggresively

gpu/command_buffer/client/query_tracker.cc

Index: gpu/command_buffer/client/query_tracker.cc
diff --git a/gpu/command_buffer/client/query_tracker.cc b/gpu/command_buffer/client/query_tracker.cc
index 285560590b34a403ba5e2abb763d8c9d340ffc8d..baf9e3d1ba6d1c3f18d50c9379f4ba3fe1cf1c08 100644
--- a/gpu/command_buffer/client/query_tracker.cc
+++ b/gpu/command_buffer/client/query_tracker.cc
@@ -93,6 +93,7 @@ QueryTracker::Query::Query(GLuint id, GLenum target,
       submit_count_(0),
       token_(0),
       flushed_(false),
+      serial_(0),
       client_begin_time_us_(0),
       result_(0) {
     }
@@ -109,13 +110,15 @@ void QueryTracker::Query::Begin(GLES2Implementation* gl) {
     case GL_LATENCY_QUERY_CHROMIUM:
       client_begin_time_us_ = MicrosecondsSinceOriginOfTime();
       // tell service about id, shared memory and count
-      gl->helper()->BeginQueryEXT(target(), id(), shm_id(), shm_offset());
+      gl->helper()->BeginQueryEXT(
+          target(), id(), serial(), shm_id(), shm_offset());
       break;
     case GL_ASYNC_PIXEL_UNPACK_COMPLETED_CHROMIUM:
     case GL_ASYNC_PIXEL_PACK_COMPLETED_CHROMIUM:
     default:
       // tell service about id, shared memory and count
-      gl->helper()->BeginQueryEXT(target(), id(), shm_id(), shm_offset());
+      gl->helper()->BeginQueryEXT(
+          target(), id(), serial(), shm_id(), shm_offset());
       break;
   }
 }
@@ -127,7 +130,8 @@ void QueryTracker::Query::End(GLES2Implementation* gl) {
       if (error == GL_NO_ERROR) {
         // There was no error so start the query on the serivce.
         // it will end immediately.
-        gl->helper()->BeginQueryEXT(target(), id(), shm_id(), shm_offset());
+        gl->helper()->BeginQueryEXT(
+            target(), id(), serial(), shm_id(), shm_offset());
       } else {
         // There's an error on the client, no need to bother the service. just
         // set the query as completed and return the error.
@@ -139,7 +143,7 @@ void QueryTracker::Query::End(GLES2Implementation* gl) {
       }
     }
   }
-  gl->helper()->EndQueryEXT(target(), submit_count());
+  gl->helper()->EndQueryEXT(target(), serial(), submit_count());
   MarkAsPending(gl->helper()->InsertToken());
 }
 
@@ -191,7 +195,8 @@ uint32 QueryTracker::Query::GetResult() const {
 }
 
 QueryTracker::QueryTracker(MappedMemoryManager* manager)
-    : query_sync_manager_(manager) {
+    : query_sync_manager_(manager),
+      next_serial_(1) {
 }
 
 QueryTracker::~QueryTracker() {
@@ -205,7 +210,8 @@ QueryTracker::~QueryTracker() {
   }
 }
 
-QueryTracker::Query* QueryTracker::CreateQuery(GLuint id, GLenum target) {
+QueryTracker::Query* QueryTracker::CreateQuery(
+    GLuint id, GLenum target) {
   DCHECK_NE(0u, id);
   FreeCompletedQueries();
   QuerySyncManager::QueryInfo info;
@@ -219,6 +225,13 @@ QueryTracker::Query* QueryTracker::CreateQuery(GLuint id, GLenum target) {
   return query;
 }
 
+QueryTracker::Query* QueryTracker::CreateInternalQuery(
+    GLuint id, GLenum target) {
+  Query* query = CreateQuery(id, target);
+  query->set_serial(NextSerial());
+  return query;
+}
+
 QueryTracker::Query* QueryTracker::GetQuery(
     GLuint client_id) {
   QueryMap::iterator it = queries_.find(client_id);
@@ -260,5 +273,12 @@ void QueryTracker::FreeCompletedQueries() {
   }
 }
 
+uint32 QueryTracker::NextSerial() {
+  uint32 serial = next_serial_++;
+  if (serial == 0)
+    return NextSerial();

[piman, 2014/01/11 02:02:32]

In case of wrap around we need to Finish().
The rest of the code assumes last_read_serial > |serial| means serial has
passed. It would not be true with this code, after wraparound.

We do Finish when tokens wrap (see CommandBufferHelper::InsertToken).

If we're worried that we might actually wrap in practice and don't want to
Finish() in that case, we can do something like double-buffer the range, and
only call Finish() if the last_read_serial has the same high bit as the new
serial, when that high bit changes. That should not happen in practice (unless
we can have 2^31 queries actually in flight).

[jadahl, 2014/01/16 16:24:39]

Will Finish() really help anything? In the version I just uploaded I simply
provide an API via CommandBufferHelper (HasSerialPassed(uint32)) that just
checks the bits.

This will work if we have less than 2^31 concurrent queries, and if we'd ever
have that many I think we have bigger problems already :)

+  return serial;
+}
+
 }  // namespace gles2
 }  // namespace gpu