1687338 - Move ScriptSource XDR-encoding to the linearize step of Stencil-XDR

Status: RESOLVED FIXED

(Core :: JavaScript Engine, task, P1)

Description

[Ted Campbell [:tcampbell]]

When encoding a script for the bytecode cache in incremental mode, we currently transcode the ScriptSource in the initial encoding. This work is done on main-thread, during page load.

Another consequence, is that since this is so early, there is rarely a chance for source compression to have taken effect (which the transcoder supports) and we end up with larger cache files and more time in IPC and I/O.

Since the incremental encoder is associated with a ScriptSource, it will still always be available to us during the linearize step. We can instead perform the encoding of scriptsource here which has numerous benefits.

• ScriptSources have more opportunities to compress
• Duplicate copies of source aren't kept in memory during page load
• If encoding is aborted before saved to cache, the scriptsource encoding is also avoided.

Comment 1

[Ted Campbell [:tcampbell]]

Attachment: Bug 1687338 - StencilXDR should defer header encoding until linearize step. r?arai!

Instead of transcoding the ScriptSource immediately when the
incremental-encoder is started, we should defer until the 'linearize' step
which still has access to the ScriptSource. This moves work from page-load to
idle, and gives the GC a chance to compress the source and reduce XDR size
(and thus IPC and I/O time).

Comment 2

[Ted Campbell [:tcampbell]]

Attachment: Bug 1687338 - Inline XDRCompilationInput into callers. r?arai!

Comment 3

[Ted Campbell [:tcampbell]]

Attachment: Bug 1687338 - Pass the ScriptSource into the XDR linearize method. r?arai!

Depends on D102231

Comment 4

[Ted Campbell [:tcampbell]]

Attachment: Bug 1687338 - Refactor XDR-Stencil header trancoding code. r?arai!

Depends on D102214

Comment 5

[Ted Campbell [:tcampbell]]

After some experimentation, it seems that source compression still occurs much later. Regardless, I think the patches will simply some code and more work out of page load, so I'll clean them up for review.

Comment 6

[Ted Campbell [:tcampbell]]

Attachment: Bug 1687338 - Transcode XDR-Stencil header directly to target buffer. r?arai!

Depends on D102233

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/1e7377b38967
Inline XDRCompilationInput into callers. r=arai
https://hg.mozilla.org/integration/autoland/rev/c67b08bb068a
Pass the ScriptSource into the XDR linearize method. r=arai
https://hg.mozilla.org/integration/autoland/rev/170807435f02
StencilXDR should defer header encoding until linearize step. r=arai
https://hg.mozilla.org/integration/autoland/rev/913817e57a91
Refactor XDR-Stencil header trancoding code. r=arai
https://hg.mozilla.org/integration/autoland/rev/5f941b574274
Transcode XDR-Stencil header directly to target buffer. r=arai

Comment 8

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/1e7377b38967
https://hg.mozilla.org/mozilla-central/rev/c67b08bb068a
https://hg.mozilla.org/mozilla-central/rev/170807435f02
https://hg.mozilla.org/mozilla-central/rev/913817e57a91
https://hg.mozilla.org/mozilla-central/rev/5f941b574274