[scheduler] CPUTimeBudgetPool: Require a minimal level of budget to run

third_party/WebKit/Source/platform/scheduler/renderer/budget_pool.h

 // Copyright 2017 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.
 
 #ifndef THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_RENDERER_BUDGET_POOL_H_
 #define THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_RENDERER_BUDGET_POOL_H_
 
 #include <unordered_set>
 
 #include "base/callback.h"
@@ skipping 66 matching lines @@
   virtual void AsValueInto(base::trace_event::TracedValue* state,
                            base::TimeTicks now) const = 0;
 };
 
 // CPUTimeBudgetPool represents a collection of task queues which share a limit
 // on total cpu time.
 class BLINK_PLATFORM_EXPORT CPUTimeBudgetPool : public BudgetPool {
  public:
   CPUTimeBudgetPool(const char* name,
                     BudgetPoolController* budget_pool_controller,
-                    base::TimeTicks now,
-                    base::Optional<base::TimeDelta> max_budget_level,
-                    base::Optional<base::TimeDelta> max_throttling_duration);
+                    base::TimeTicks now);
 
   ~CPUTimeBudgetPool();
 
+  // Set max budget level, base::nullopt represent absence of max level.
+  // Max budget level prevents accumulating arbitrary large budgets when
+  // page is inactive for a very long time.
+  void SetMaxBudgetLevel(base::TimeTicks now,
+                         base::Optional<base::TimeDelta> max_budget_level);
+
+  // Set max throttling duration, base::nullopt represents absense of it.
+  // Max throttling duration prevents page from being throttled for
+  // a very long period after a single long task.
+  void SetMaxThrottlingDelay(
+      base::TimeTicks now,
+      base::Optional<base::TimeDelta> max_throttling_delay);
+
+  // Set minimal budget level required to run a task. If budget pool was
+  // exhausted, it needs to accumulate at least |min_budget_to_run| time units
+  // to run tasks again.
+  // It still can run tasks when budget is positive but less than this level.

[alex clarke (OOO till 29th), 2017/03/20 09:03:03]

This sentence seems to state the opposite of the previous one, could you perhaps
elaborate a bit?

[altimin, 2017/03/20 15:21:08]

Done.

+  // This is needed for integration with WakeupBudgetPool to prevent a situation
+  // when wakeup happened but time budget pool allows only one task to run at
+  // the moment.
+  // It is recommended to use the same value for this and WakeupBudgetPool's
+  // wakeup window length.
+  void SetMinBudgetLevelToRun(base::TimeTicks now,
+                              base::TimeDelta min_budget_level_to_run);
+
   // Throttle task queues from this time budget pool if tasks are running
   // for more than |cpu_percentage| per cent of wall time.
   // This function does not affect internal time budget level.
   void SetTimeBudgetRecoveryRate(base::TimeTicks now, double cpu_percentage);
 
   // Increase budget level by given value. This function DOES NOT unblock
   // queues even if they are allowed to run with increased budget level.
   void GrantAdditionalBudget(base::TimeTicks now, base::TimeDelta budget_level);
 
   // Set callback which will be called every time when this budget pool
@@ skipping 32 matching lines @@
   void EnforceBudgetLevelRestrictions();
 
   const char* name_;  // NOT OWNED
 
   BudgetPoolController* budget_pool_controller_;
 
   // Max budget level which we can accrue.
   // Tasks will be allowed to run for this time before being throttled
   // after a very long period of inactivity.
   base::Optional<base::TimeDelta> max_budget_level_;
-  // Max throttling duration places a lower limit on time budget level,
+  // Max throttling delay places a lower limit on time budget level,
   // ensuring that one long task does not cause extremely long throttling.
   // Note that this is not the guarantee that every task will run

[alex clarke (OOO till 29th), 2017/03/20 09:03:03]

... is not _a_ guarantee that ...

[altimin, 2017/03/20 15:21:08]

Done.

   // after desired run time + max throttling duration, but a guarantee
-  // that at least one task will be run every max_throttling_duration.
-  base::Optional<base::TimeDelta> max_throttling_duration_;
+  // that at least one task will be run every max_throttling_delay.
+  base::Optional<base::TimeDelta> max_throttling_delay_;
+  // Minimal budget required to be accumulated after queue is blocked

[alex clarke (OOO till 29th), 2017/03/20 09:03:03]

Could you please reword? I found this sentence confusing.   s/Minimal/Minimum

[altimin, 2017/03/20 15:21:08]

Done.

+  // to prevent queue from being immediately blocked after one small task.
+  base::TimeDelta min_budget_level_to_run_;
 
   base::TimeDelta current_budget_level_;
   base::TimeTicks last_checkpoint_;
   double cpu_percentage_;
   bool is_enabled_;
 
   std::unordered_set<TaskQueue*> associated_task_queues_;
 
   base::Callback<void(base::TimeDelta)> reporting_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(CPUTimeBudgetPool);
 };
 
 }  // namespace scheduler
 }  // namespace blink
 
 #endif  // THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_RENDERER_BUDGET_POOL_H_