Ensure black and gray objects are kept around by scavenger

Ensure black and gray objects are kept around by scavenger

Currently, scavenger can collect objects marked by MarkCompact as black or grey.
For black objects it does no postprocessing, just collects them. For grey
objects scavenger removes dead objects from the marking queue (while updating
old pointers to forwarding pointers in the queue).

This cl ensures that black and grey objects are kept alive by the scavenger. 
This is an expected invariant, very much worth having.

As multiple scavenges usually run during single incremental marking, which would copy objects once to the other semispace, and then once to the old space, we promote objects immediately.

LOG=no

[Marcel Hlopko, 2016-05-17 10:37:15]

hlopko@chromium.org changed reviewers:
+ hpayer@chromium.org, mlippautz@chromium.org

[Marcel Hlopko, 2016-05-17 10:39:31]

Ptal. This cl can cause performance regression (we copy more stuff during
scavenge) what is the correct process to land this? Just land and see if bots
get angry? :) Thanks!

[Marcel Hlopko, 2016-05-17 10:45:19]

Patchset #1 (id:1) has been deleted

[Marcel Hlopko, 2016-05-17 10:45:23]

Patchset #1 (id:20001) has been deleted

[Marcel Hlopko, 2016-05-17 10:45:28]

Patchset #1 (id:40001) has been deleted

[Marcel Hlopko, 2016-05-17 10:45:32]

Patchset #1 (id:60001) has been deleted

[Marcel Hlopko, 2016-05-17 10:46:01]

Removing unreachable branch in IncrementalMarking. Can the remaining branch be
reached?

[Marcel Hlopko, 2016-05-17 11:40:15]

So the if branch removal was too ambitious, reverting.

[Marcel Hlopko, 2016-05-17 17:32:11]

Some numbers to consider. On my machine the reviving phase alone makes for
0.06ms on average (when moved to the end of scavenging):

  len: 316
  min: 0.0
  max: 0.19
  avg: 0.0631012658228
  [0,5[: 316
  95.0%: 0.11
  97.0%: 0.13
  98.0%: 0.13
  99.0%: 0.15

That's 3% worse for scavenger total time, 2.35% worse on average, 6.5% worse on
the max case.

[Marcel Hlopko, 2016-05-17 17:38:35]

Added printing using --print_nvp

[Marcel Hlopko, 2016-05-18 19:16:47]

Description was changed from

==========
Ensure black and gray objects are kept around by scavenger

Currently, scavenger can collect objects marked by MarkCompact as black or grey.
For black objects it does no postprocessing, just collects them. For grey
objects scavenger removes dead objects from the marking queue (while updating
old pointers to forwarding pointers in the queue).

This cl ensures that black and grey objects are kept alive by the scavenger.

LOG=no
==========

to

==========
Ensure black and gray objects are kept around by scavenger

Currently, scavenger can collect objects marked by MarkCompact as black or grey.
For black objects it does no postprocessing, just collects them. For grey
objects scavenger removes dead objects from the marking queue (while updating
old pointers to forwarding pointers in the queue).

This cl ensures that black and grey objects are kept alive by the scavenger.
This is an expected invariant, very much worth having.

LOG=no
==========

[Marcel Hlopko, 2016-05-19 16:44:43]

Description was changed from

==========
Ensure black and gray objects are kept around by scavenger

Currently, scavenger can collect objects marked by MarkCompact as black or grey.
For black objects it does no postprocessing, just collects them. For grey
objects scavenger removes dead objects from the marking queue (while updating
old pointers to forwarding pointers in the queue).

This cl ensures that black and grey objects are kept alive by the scavenger.
This is an expected invariant, very much worth having.

LOG=no
==========

to

==========
Ensure black and gray objects are kept around by scavenger

Currently, scavenger can collect objects marked by MarkCompact as black or grey.
For black objects it does no postprocessing, just collects them. For grey
objects scavenger removes dead objects from the marking queue (while updating
old pointers to forwarding pointers in the queue).

This cl ensures that black and grey objects are kept alive by the scavenger. 
This is an expected invariant, very much worth having.

LOG=no
==========

[Hannes Payer (out of office), 2016-05-20 07:34:41]

Looking good, just nits. Let's look at perf numbers.

https://codereview.chromium.org/1988623002/diff/220001/src/heap/heap.cc
File src/heap/heap.cc (right):

https://codereview.chromium.org/1988623002/diff/220001/src/heap/heap.cc#newco...
src/heap/heap.cc:1699: // Copy objects marked black or grey by MarkCompact
collector.
Scavenge objects...

https://codereview.chromium.org/1988623002/diff/220001/src/heap/heap.h
File src/heap/heap.h (right):

https://codereview.chromium.org/1988623002/diff/220001/src/heap/heap.h#newcod...
src/heap/heap.h:1075: void IterateMarkedForScavenger(ObjectVisitor* v);
IterateMarkedObjects

https://codereview.chromium.org/1988623002/diff/220001/src/heap/mark-compact.h
File src/heap/mark-compact.h (right):

https://codereview.chromium.org/1988623002/diff/220001/src/heap/mark-compact....
src/heap/mark-compact.h:160: // Returns true if the transferred color is black.
Mention that this function clears the color of the source object.

[Marcel Hlopko, 2016-05-20 08:43:58]

Patchset #9 (id:240001) has been deleted

[Marcel Hlopko, 2016-05-20 14:31:41]

Let's discuss tradeoffs offline on Monday.

https://codereview.chromium.org/1988623002/diff/220001/src/heap/heap.cc
File src/heap/heap.cc (right):

https://codereview.chromium.org/1988623002/diff/220001/src/heap/heap.cc#newco...
src/heap/heap.cc:1699: // Copy objects marked black or grey by MarkCompact
collector.
Done.

https://codereview.chromium.org/1988623002/diff/220001/src/heap/heap.h
File src/heap/heap.h (right):

https://codereview.chromium.org/1988623002/diff/220001/src/heap/heap.h#newcod...
src/heap/heap.h:1075: void IterateMarkedForScavenger(ObjectVisitor* v);
Done.

https://codereview.chromium.org/1988623002/diff/220001/src/heap/mark-compact.h
File src/heap/mark-compact.h (right):

https://codereview.chromium.org/1988623002/diff/220001/src/heap/mark-compact....
src/heap/mark-compact.h:160: // Returns true if the transferred color is black.
Done.

[Marcel Hlopko, 2016-05-23 12:26:34]

hlopko@chromium.org changed reviewers:
+ ulan@chromium.org

[Marcel Hlopko, 2016-05-24 11:55:49]

Description was changed from

==========
Ensure black and gray objects are kept around by scavenger

Currently, scavenger can collect objects marked by MarkCompact as black or grey.
For black objects it does no postprocessing, just collects them. For grey
objects scavenger removes dead objects from the marking queue (while updating
old pointers to forwarding pointers in the queue).

This cl ensures that black and grey objects are kept alive by the scavenger. 
This is an expected invariant, very much worth having.

LOG=no
==========

to

==========
Ensure black and gray objects are kept around by scavenger

Currently, scavenger can collect objects marked by MarkCompact as black or grey.
For black objects it does no postprocessing, just collects them. For grey
objects scavenger removes dead objects from the marking queue (while updating
old pointers to forwarding pointers in the queue).

This cl ensures that black and grey objects are kept alive by the scavenger. 
This is an expected invariant, very much worth having.

As multiple scavenges usually run during single incremental marking, which would
copy objects once to the other semispace, and then once to the old space, we
promote objects immediately.

LOG=no
==========