Initialize TaskScheduler with InitParams in CreateAndSetSimpleTaskScheduler().

base/task_scheduler/task_scheduler.cc

Index: base/task_scheduler/task_scheduler.cc
diff --git a/base/task_scheduler/task_scheduler.cc b/base/task_scheduler/task_scheduler.cc
index bff2de65a422e5be152e8d4b1b29f9233fd127da..69a1a5ff8db6a98176cc23884706213f0cef1b71 100644
--- a/base/task_scheduler/task_scheduler.cc
+++ b/base/task_scheduler/task_scheduler.cc
@@ -9,6 +9,7 @@
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/sys_info.h"
+#include "base/task_scheduler/initialization_util.h"
 #include "base/task_scheduler/scheduler_worker_pool_params.h"
 #include "base/task_scheduler/task_scheduler_impl.h"
 #include "base/threading/platform_thread.h"
@@ -40,16 +41,39 @@ TaskScheduler::InitParams::~InitParams() = default;
 #if !defined(OS_NACL)
 // static
 void TaskScheduler::CreateAndSetSimpleTaskScheduler(const std::string& name) {
-  constexpr int kMinNumThreads = 1;
-  std::vector<SchedulerWorkerPoolParams> worker_pool_params_vector;
-  worker_pool_params_vector.emplace_back(
-      name, ThreadPriority::NORMAL,
-      SchedulerWorkerPoolParams::StandbyThreadPolicy::LAZY,
-      std::max(kMinNumThreads, SysInfo::NumberOfProcessors()),
-      TimeDelta::FromSeconds(30));
+  using StandbyThreadPolicy = SchedulerWorkerPoolParams::StandbyThreadPolicy;
+
+  constexpr TimeDelta kSuggestedReclaimTime = TimeDelta::FromSeconds(30);
+  constexpr int kMaxNumBackgroundThreads = 1;
+  constexpr int kMaxNumBackgroundBlockingThreads = 2;
+  constexpr int kMaxNumForegroundThreadsLowerBound = 2;
+  constexpr int kMaxNumForegroundThreadsUpperBound = 32;
+  constexpr double kMaxNumForegroundThreadsCoresMultiplier = 1;
+  constexpr int kMaxNumForegroundThreadsOffset = 0;
+  constexpr int kMaxNumForegroundBlockingThreadsLowerBound = 2;
+  constexpr int kMaxNumForegroundBlockingThreadsUpperBound = 64;

[gab, 2017/04/04 20:48:13]

Why 32 and 64? Seems very high for a "simple" task scheduler.

[fdoray, 2017/04/05 13:01:28]

My thinking was that someone instantiating a simple task scheduler could want to
use all the cores (it's what Windows Thread Pool does). The 32/64 maximums could
even be higher (I don't want them to be hit on most machines).

What constants would you use?

[robliao, 2017/04/05 23:06:56]

An alternative way to go about this is to adjust using the multiplier. Maybe we
want the Sum(All multipliers) <= 1 as that would mean we would have the
num_of_cores or fewer threads. This would make the upperbounds a little less
important, but still useful for those machines that have lots of cores.

+  constexpr double kMaxNumForegroundBlockingThreadsCoresMultiplier = 2;

[gab, 2017/04/06 15:14:52]

This isn't a MaxNum, it's a multiplier only, right?

How about naming the constants:

k(PoolName)(MaxUpperBound|MaxLowerBound|CoresMultiplier|Offset)?

Also, PS: will we really ever care about |offset| param? It's never been
anything but 0 so far...

+  constexpr int kMaxNumForegroundBlockingThreadsOffset = 0;
+
   CreateAndSetDefaultTaskScheduler(
-      worker_pool_params_vector,
-      Bind([](const TaskTraits&) -> size_t { return 0; }));
+      name, {{StandbyThreadPolicy::LAZY, kMaxNumBackgroundThreads,
+              kSuggestedReclaimTime},
+             {StandbyThreadPolicy::LAZY, kMaxNumBackgroundBlockingThreads,
+              kSuggestedReclaimTime},
+             {StandbyThreadPolicy::LAZY,
+              RecommendedMaxNumberOfThreadsInPool(
+                  kMaxNumForegroundThreadsLowerBound,
+                  kMaxNumForegroundThreadsUpperBound,
+                  kMaxNumForegroundThreadsCoresMultiplier,
+                  kMaxNumForegroundThreadsOffset),
+              kSuggestedReclaimTime},
+             {StandbyThreadPolicy::LAZY,
+              RecommendedMaxNumberOfThreadsInPool(
+                  kMaxNumForegroundBlockingThreadsLowerBound,
+                  kMaxNumForegroundBlockingThreadsUpperBound,
+                  kMaxNumForegroundBlockingThreadsCoresMultiplier,
+                  kMaxNumForegroundBlockingThreadsOffset),
+              kSuggestedReclaimTime}});
 }
 #endif  // !defined(OS_NACL)