Increase the number of TaskScheduler foreground threads in renderers.

content/renderer/render_process_impl.cc

 // Copyright (c) 2012 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 "content/renderer/render_process_impl.h"
 
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
@@ skipping 75 matching lines @@
 GetDefaultSchedulerWorkerPoolParams() {
   using StandbyThreadPolicy =
       base::SchedulerWorkerPoolParams::StandbyThreadPolicy;
   using ThreadPriority = base::ThreadPriority;
   constexpr size_t kMaxNumThreadsInBackgroundPool = 1;
   constexpr size_t kMaxNumThreadsInBackgroundFileIOPool = 1;
   constexpr int kMaxNumThreadsInForegroundPoolLowerBound = 2;
   constexpr int kMaxNumThreadsInForegroundPoolUpperBound = 4;
   constexpr double kMaxNumThreadsInForegroundPoolCoresMultiplier = 1;
   constexpr int kMaxNumThreadsInForegroundPoolOffset = 0;
-  constexpr size_t kMaxNumThreadsInForegroundFileIOPool = 1;
   constexpr auto kSuggestedReclaimTime = base::TimeDelta::FromSeconds(30);
 
   std::vector<base::SchedulerWorkerPoolParams> params_vector;
   params_vector.emplace_back("RendererBackground", ThreadPriority::BACKGROUND,
                              StandbyThreadPolicy::LAZY,
                              kMaxNumThreadsInBackgroundPool,
                              kSuggestedReclaimTime);
   params_vector.emplace_back(
       "RendererBackgroundFileIO", ThreadPriority::BACKGROUND,
       StandbyThreadPolicy::LAZY, kMaxNumThreadsInBackgroundFileIOPool,
       kSuggestedReclaimTime);
   params_vector.emplace_back("RendererForeground", ThreadPriority::NORMAL,
                              StandbyThreadPolicy::LAZY,
                              base::RecommendedMaxNumberOfThreadsInPool(
                                  kMaxNumThreadsInForegroundPoolLowerBound,
                                  kMaxNumThreadsInForegroundPoolUpperBound,
                                  kMaxNumThreadsInForegroundPoolCoresMultiplier,
                                  kMaxNumThreadsInForegroundPoolOffset),
                              kSuggestedReclaimTime);
+
+  // V8Platform::CallOnBackgroundThread() posts foreground blocking tasks. It
+  // expects to have as many threads as cores available for these tasks.

[gab, 2017/02/06 21:17:10]

Such a comment is fine to justify CL (i.e. in desc) but doesn't belong in this
top-level code IMO.

Also, why are these blocking? Blocking + flooding cores with work doesn't
typically go together?

[fdoray, 2017/02/09 13:32:13]

Done. The v8 tasks are only blocking in tests.

+  const int max_num_foreground_file_io_threads =

[gab, 2017/02/06 21:17:10]

s/file_io/blocking/ now

[fdoray, 2017/02/09 13:32:14]

Taken care of in a separate CL https://codereview.chromium.org/2625213003/

+      std::max(2, base::SysInfo::NumberOfProcessors());
   params_vector.emplace_back("RendererForegroundFileIO", ThreadPriority::NORMAL,
                              StandbyThreadPolicy::LAZY,
-                             kMaxNumThreadsInForegroundFileIOPool,
+                             max_num_foreground_file_io_threads,
                              kSuggestedReclaimTime);
   DCHECK_EQ(WORKER_POOL_COUNT, params_vector.size());
   return params_vector;
 }
 
 // Returns the worker pool index for |traits| defaulting to FOREGROUND or
 // FOREGROUND_FILE_IO on any other priorities based off of worker pools defined
 // in GetDefaultSchedulerWorkerPoolParams().
 size_t DefaultRendererWorkerPoolIndexForTraits(const base::TaskTraits& traits) {
   const bool is_background =
@@ skipping 102 matching lines @@
     index_to_traits_callback =
         base::Bind(&DefaultRendererWorkerPoolIndexForTraits);
   }
   DCHECK(index_to_traits_callback);
 
   base::TaskScheduler::CreateAndSetDefaultTaskScheduler(
       params_vector, index_to_traits_callback);
 }
 
 }  // namespace content