1816340 - Emergency GCs should wait for background free

Status: RESOLVED FIXED

(Core :: JavaScript: GC, task, P1)

Description

[Paul Bone [:pbone]]

I was looking at AWSY results and thought I saw a problem with the measurements taken after a GC. I was concerned that the GC doesn't wait for the free task to finish and the measurement can race with the free task. Free tasks are usually started by minor GCs but can also be started after sweeping. I wrote some patches to investigate and found that they made no difference to AWSY results, however they may still be a good idea since they should free more memory synchronously for emergency GCs.

AWSY results: https://treeherder.mozilla.org/perfherder/compare?originalProject=try&originalRevision=13649bc3dfdb3c1ab04a6e72405b0cc9f33e5994&newProject=try&newRevision=f783c181d6cd6f10e3d7c09679697ad6363fe8c6&framework=4&page=1&showOnlyComparable=1

Comment 1

[Paul Bone [:pbone]]

Attachment: Bug 1816340 - pt 1. Add a locked version of runFromMainThread() r=jonco

Comment 2

[Paul Bone [:pbone]]

Attachment: Bug 1816340 - pt 2. The nursery should wait for the free task on emergency GCs r=jonco

Depends on D169578

Comment 3

[Paul Bone [:pbone]]

Attachment: Bug 1816340 - pt 2. Start background free after purge r=jonco

The purgeRuntime() call can add lifo blocks to be freed by the free task.
So we should start the free task after adding this call so it has a
better chance of freeing all the lifo blocks.

Depends on D169579

Comment 4

[Paul Bone [:pbone]]

Attachment: Bug 1816340 - pt 3. Free on main thread for non-incremental GCs r=jonco

Do any off-thread freeing work created by sweeping on the main thread during
non-incremental GCs, to ensure that the work completes by the end of the GC.

Depends on D169580

Comment 5

[Paul Bone [:pbone]]

Attachment: Bug 1816340 - pt 4. Delete some dead code r=jonco

Depends on D169581

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/0618800d5910
pt 1. Add a locked version of runFromMainThread() r=jonco
https://hg.mozilla.org/integration/autoland/rev/709c4be1e56f
pt 2. Start background free after purge r=jonco
https://hg.mozilla.org/integration/autoland/rev/b32dfa568997
pt 3. Free on main thread for non-incremental GCs r=jonco
https://hg.mozilla.org/integration/autoland/rev/1a6c81eba852
pt 4. Delete some dead code r=jonco

Comment 7

[Marian-Vasile Laza]

https://hg.mozilla.org/mozilla-central/rev/0618800d5910
https://hg.mozilla.org/mozilla-central/rev/709c4be1e56f
https://hg.mozilla.org/mozilla-central/rev/b32dfa568997
https://hg.mozilla.org/mozilla-central/rev/1a6c81eba852