Fix the new generation growth criterion so it is not mislead into performing two growths in a row.

Fix the new generation growth criterion so it is not mislead into performing two growths in a row.

The decision to grow is based on the fraction of the objects that became garbage in the previous scavenge. If the previous scavenge included a growth, the new size of new space does not affect this statistic. If the program's allocation pattern remains the same, the next scavenge will see the same garbage ratio and decide to grow again, even if we would have hit the desired garbage fraction at the current capacity. This CL changes the garbage fraction to use the post-growth capcity as the dominator to prevent this eager double-growth.

This change causes Flutter Gallery to stablize at a 4MB semispace instead of 16MB, with ~10ms instead of ~40ms scavenges while interacting with the time picker on a Nexus 4.

R=danunez@google.com

Committed: https://github.com/dart-lang/sdk/commit/878a5f26537ec80a78a36707d46f54a2da4ab1ed

[rmacnak, 2017-08-21 18:27:27]

rmacnak@google.com changed reviewers:
+ asiva@google.com, danunez@google.com

[danunez, 2017-08-21 18:36:20]

lgtm w/ comments

https://codereview.chromium.org/3003063002/diff/1/runtime/vm/scavenger.h
File runtime/vm/scavenger.h (right):

https://codereview.chromium.org/3003063002/diff/1/runtime/vm/scavenger.h#newc...
runtime/vm/scavenger.h:86: // garabge to give the scavenger a chance to stablize
at the new capacity.
garabge ==> garbage

[rmacnak, 2017-08-22 22:08:45]

https://codereview.chromium.org/3003063002/diff/1/runtime/vm/scavenger.h
File runtime/vm/scavenger.h (right):

https://codereview.chromium.org/3003063002/diff/1/runtime/vm/scavenger.h#newc...
runtime/vm/scavenger.h:86: // garabge to give the scavenger a chance to stablize
at the new capacity.
On 2017/08/21 18:36:19, danunez wrote:
> garabge ==> garbage

Done.

[rmacnak, 2017-08-22 22:10:22]

Description was changed from

==========
Fix the new generation growth criterion so it is not mislead into performing two
growths in a row.

The decision to grow is based on the fraction of the objects that became garbage
in the previous scavenge. If the previous scavenge included a growth, the new
size of new space does not affect this statistic. If the program's allocation
pattern remains the same, the next scavenge will see the same garbage ratio and
decide to grow again, even if we would have hit the desired garbage fraction at
the current capacity. This CL changes the garbage fraction to use the
post-growth capcity as the dominator to prevent this eager double-growth.

This change causes Flutter Gallery to stablize at a 4MB semispace instead of
16MB, with ~10ms instead of ~40ms scavenges while interacting with the time
picker on a Nexus 4.
==========

to

==========
Fix the new generation growth criterion so it is not mislead into performing two
growths in a row.

The decision to grow is based on the fraction of the objects that became garbage
in the previous scavenge. If the previous scavenge included a growth, the new
size of new space does not affect this statistic. If the program's allocation
pattern remains the same, the next scavenge will see the same garbage ratio and
decide to grow again, even if we would have hit the desired garbage fraction at
the current capacity. This CL changes the garbage fraction to use the
post-growth capcity as the dominator to prevent this eager double-growth.

This change causes Flutter Gallery to stablize at a 4MB semispace instead of
16MB, with ~10ms instead of ~40ms scavenges while interacting with the time
picker on a Nexus 4.

R=danunez@google.com

Committed:
https://github.com/dart-lang/sdk/commit/878a5f26537ec80a78a36707d46f54a2da4ab1ed
==========

[rmacnak, 2017-08-22 22:10:24]

Committed patchset #2 (id:20001) manually as
878a5f26537ec80a78a36707d46f54a2da4ab1ed (presubmit successful).