1509322 - Relax some ChunkPool assertions

Status: RESOLVED FIXED

(Core :: JavaScript: GC, enhancement, P3)

Description

[Jon Coppeard (:jonco)]

I was investigating what happens when we hit our GC heap limit (in connection with bug 1509318) and saw a very slow shutdown GCs in an optdebug build.

A script to allocate nearly 4GiB of data and the release it took ~20 seconds to allocate and ~15 minutes to free it again.

It seems like the ChunkPool assertions have some quadratic behaviour.

Comment 1

[Jon Coppeard (:jonco)]

Attachment: bug1509322-chunkpool-assertions

We have contains() and verify() methods that are used on ChunkPools, both of which are linear in the number of chunks in the pool.

I removed verify() from push() and remove() - this still gets called in a few places during GC, just not every time we manipulate the pool.  I also removed a couple of calls to contains() in Chunk::updateChunkListAfterFree() on the grounds that if a chunk is found in one pool is unlikely to be in either of the other pools unless something is broken.

GC now takes only a few seconds in an optdebug build.

Comment 2

[Jon Coppeard (:jonco)]

Comment on attachment 9026971 [details] [diff] [review]
bug1509322-chunkpool-assertions

Shifting review due to Thanksgiving.

Comment 3

[Paul Bone [:pbone]]

Comment on attachment 9026971 [details] [diff] [review]
bug1509322-chunkpool-assertions

Review of attachment 9026971 [details] [diff] [review]:
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Thanks makes sense, thanks.

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/2094cc4738e8
Relax some ChunkPool assertions which could make debug build GCs very slow r=pbone

Comment 5

[Bogdan Tara[:bogdan_tara | bogdant]]

https://hg.mozilla.org/mozilla-central/rev/2094cc4738e8