Increase the number of TaskScheduler foreground threads in renderers.

content/renderer/render_process_impl.cc

Index: content/renderer/render_process_impl.cc
diff --git a/content/renderer/render_process_impl.cc b/content/renderer/render_process_impl.cc
index db042b903f1748a8b4ff9fbb4e92f0b3bb048555..abb54655863198d93a2eabcf1c80dbbb18bebae8 100644
--- a/content/renderer/render_process_impl.cc
+++ b/content/renderer/render_process_impl.cc
@@ -93,7 +93,14 @@ GetDefaultSchedulerWorkerPoolParams() {
   constexpr int kMaxNumThreadsInForegroundPoolUpperBound = 4;
   constexpr double kMaxNumThreadsInForegroundPoolCoresMultiplier = 1;
   constexpr int kMaxNumThreadsInForegroundPoolOffset = 0;
-  constexpr size_t kMaxNumThreadsInForegroundFileIOPool = 1;
+
+  // V8Platform::CallOnBackgroundThread() posts foreground blocking tasks. It
+  // expects to have as many threads as cores available for these tasks.
+  constexpr int kMaxNumThreadsInForegroundFileIOPoolLowerBound = 2;
+  constexpr int kMaxNumThreadsInForegroundFileIOPoolUpperBound = 128;
+  constexpr double kMaxNumThreadsInForegroundFileIOPoolCoresMultiplier = 1;
+  constexpr int kMaxNumThreadsInForegroundFileIOPoolOffset = 0;
+
   constexpr auto kSuggestedReclaimTime = base::TimeDelta::FromSeconds(30);
 
   std::vector<base::SchedulerWorkerPoolParams> params_vector;
@@ -113,10 +120,15 @@ GetDefaultSchedulerWorkerPoolParams() {
                                  kMaxNumThreadsInForegroundPoolCoresMultiplier,
                                  kMaxNumThreadsInForegroundPoolOffset),
                              kSuggestedReclaimTime);
-  params_vector.emplace_back("RendererForegroundFileIO", ThreadPriority::NORMAL,
-                             StandbyThreadPolicy::LAZY,
-                             kMaxNumThreadsInForegroundFileIOPool,
-                             kSuggestedReclaimTime);
+  params_vector.emplace_back(
+      "RendererForegroundFileIO", ThreadPriority::NORMAL,
+      StandbyThreadPolicy::LAZY,
+      base::RecommendedMaxNumberOfThreadsInPool(

[robliao, 2017/02/06 20:07:51]

Is using RecommendedMax... better than a std::min(2,
SysInfo::NumberOfProcessors())?

This way we don't have to specify a fake upper bound.

[fdoray, 2017/02/06 20:14:03]

Done.

+          kMaxNumThreadsInForegroundFileIOPoolLowerBound,
+          kMaxNumThreadsInForegroundFileIOPoolUpperBound,
+          kMaxNumThreadsInForegroundFileIOPoolCoresMultiplier,
+          kMaxNumThreadsInForegroundFileIOPoolOffset),
+      kSuggestedReclaimTime);
   DCHECK_EQ(WORKER_POOL_COUNT, params_vector.size());
   return params_vector;
 }