Add canExceedIdleDeadlineIfRequired function to Scheduler and use it in Oilpan

Add canExceedIdleDeadlineIfRequired function to Scheduler and use it in Oilpan.

Adds a canExceedIdleDeadlineIfRequired function to the Scheduler to enable 
IdleTasks to estimate the best time for them to exceed their deadline
if they have a large monolithic task which could not be run otherwise. 

Modifies the Oilpan performIdleTask to perform the GC if
it would exceed it's deadline
but the scheduler returns true from canExceedIdleDeadlineIfRequired.

Chromium side of patch: https://codereview.chromium.org/969373002/edit

Long idle task design doc:
https://docs.google.com/a/chromium.org/document/d/1yBlUdYW8VTIfB-DqhvQqUeP0kf-Ap1W4cao2yQq58Do/edit

BUG=455713
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=192006

[rmcilroy, 2015-03-03 12:37:47]

rmcilroy@chromium.org changed reviewers:
+ haraken@chromium.org, kouhei@chromium.org, skyostil@chromium.org

[rmcilroy, 2015-03-03 12:37:48]

haraken@ / kouhei@: Please take a look at the Oilpan change.

Sami: Please take a look at the scheduler changes.

[haraken, 2015-03-03 15:10:39]

LGTM

As kouhei mentioned in #5 in https://codereview.chromium.org/965283002/, the
current heuristic  (i.e, idleDeltaInSeconds <= Heap::estimatedMarkingTime()) is
not working as expected. So this CL is not nice in a sense that it's going to
add another heuristic on the uncertain heuristic. However, I'm fine with this at
the moment because performIdleGC() is enabled only in oilpan builds and
kouhei-san has a plan to investigate and optimize the heuristics in the near
future.

https://codereview.chromium.org/971283002/diff/1/Source/platform/heap/ThreadS...
File Source/platform/heap/ThreadState.cpp (right):

https://codereview.chromium.org/971283002/diff/1/Source/platform/heap/ThreadS...
Source/platform/heap/ThreadState.cpp:732: if (idleDeltaInSeconds <=
Heap::estimatedMarkingTime() &&
!Scheduler::shared()->isMaximumIdleDeadline(deadlineSeconds)) {

Shall we add a comment on what this branch is doing?

https://codereview.chromium.org/971283002/diff/1/Source/platform/heap/ThreadS...
Source/platform/heap/ThreadState.cpp:737: // FIXME: Make this precise once idle
task is guaranteed to be not in nested loop.

Ross, Sami: Not related to this CL, is this FIXME not yet fixed?

[rmcilroy, 2015-03-03 15:20:02]

https://codereview.chromium.org/971283002/diff/1/Source/platform/heap/ThreadS...
File Source/platform/heap/ThreadState.cpp (right):

https://codereview.chromium.org/971283002/diff/1/Source/platform/heap/ThreadS...
Source/platform/heap/ThreadState.cpp:737: // FIXME: Make this precise once idle
task is guaranteed to be not in nested loop.
On 2015/03/03 15:10:39, haraken wrote:
> 
> Ross, Sami: Not related to this CL, is this FIXME not yet fixed?

I'm working on this right now - I'll let you know when I have a WIP CL.

[rmcilroy, 2015-03-03 19:39:09]

https://codereview.chromium.org/971283002/diff/1/Source/platform/heap/ThreadS...
File Source/platform/heap/ThreadState.cpp (right):

https://codereview.chromium.org/971283002/diff/1/Source/platform/heap/ThreadS...
Source/platform/heap/ThreadState.cpp:737: // FIXME: Make this precise once idle
task is guaranteed to be not in nested loop.
On 2015/03/03 15:20:01, rmcilroy wrote:
> On 2015/03/03 15:10:39, haraken wrote:
> > 
> > Ross, Sami: Not related to this CL, is this FIXME not yet fixed?
> 
> I'm working on this right now - I'll let you know when I have a WIP CL.

CL is up at https://codereview.chromium.org/976723002/

[kouhei (in TOK), 2015-03-04 08:25:45]

lgtm

I think we should proceed with this landing now.
The heuristics in my CL is not directly related to this CL.

[rmcilroy, 2015-03-17 10:33:29]

rmcilroy@chromium.org changed reviewers:
+ jochen@chromium.org

[rmcilroy, 2015-03-17 10:33:30]

Rebased and changed API to canExceedIdleDeadlineIfRequired - PTAL.

Jochen: PTAL at public/platform/WebScheduler.h, thanks.

https://codereview.chromium.org/971283002/diff/1/Source/platform/heap/ThreadS...
File Source/platform/heap/ThreadState.cpp (right):

https://codereview.chromium.org/971283002/diff/1/Source/platform/heap/ThreadS...
Source/platform/heap/ThreadState.cpp:732: if (idleDeltaInSeconds <=
Heap::estimatedMarkingTime() &&
!Scheduler::shared()->isMaximumIdleDeadline(deadlineSeconds)) {
On 2015/03/03 15:10:39, haraken wrote:
> 
> Shall we add a comment on what this branch is doing?

Done.

[jochen (gone - plz use gerrit), 2015-03-17 10:37:05]

lgtm

[kouhei (in TOK), 2015-03-17 10:37:30]

lgtm

https://codereview.chromium.org/971283002/diff/20001/Source/platform/heap/Thr...
File Source/platform/heap/ThreadState.cpp (right):

https://codereview.chromium.org/971283002/diff/20001/Source/platform/heap/Thr...
Source/platform/heap/ThreadState.cpp:596: // exceed the deadline, the reschedule
for the next idle period.
s/the/then?

[rmcilroy, 2015-03-17 10:55:25]

https://codereview.chromium.org/971283002/diff/20001/Source/platform/heap/Thr...
File Source/platform/heap/ThreadState.cpp (right):

https://codereview.chromium.org/971283002/diff/20001/Source/platform/heap/Thr...
Source/platform/heap/ThreadState.cpp:596: // exceed the deadline, the reschedule
for the next idle period.
On 2015/03/17 10:37:30, kouhei wrote:
> s/the/then?

Done.

[rmcilroy, 2015-03-17 10:55:34]

The CQ bit was checked by rmcilroy@chromium.org

[rmcilroy, 2015-03-17 10:55:34]

The patchset sent to the CQ was uploaded after l-g-t-m from
haraken@chromium.org, jochen@chromium.org, kouhei@chromium.org
Link to the patchset: https://codereview.chromium.org/971283002/#ps40001 (title:
"Fix Typo")

[commit-bot: I haz the power, 2015-03-17 10:55:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/971283002/40001

[commit-bot: I haz the power, 2015-03-17 12:37:43]

Committed patchset #3 (id:40001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=192006