1957504 - wasm: enable lazy tiering for all content

Status: RESOLVED FIXED

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

Description

[Ryan Hunt [:rhunt]]

We believe that enabling lazy tiering for all content (not just GC modules) will improve startup time and also peak performance through support for inlining.

For shipping this, we need to:

1. Flip the 'lazy_tiering' pref to true [1]
2. Disable lazy tiering when the 'test serialization' pref is turned on [2]. This will keep us testing serialization by falling back to eager compilation.

We probably also want to:

1. Decide what to do if we don't have helper threads available. Right now we will disable tiering and fall back to a 'once' compilation [3]. We possibly could fall back to synchronous compilation in that case. That is how JS works, if I understand correctly.
2. (pre-existing) Ensure that CanFlushExecutionContextForAllThreads is thread safe. It looks like there is a race condition in the function around 'computed' and 'hasMembarrier'.

As a follow up once lazy tiering for all content has been shipped in a release or two, we should replace the two lazy tiering prefs with an 'eager' tiering pref that is off by default.

[1] https://searchfox.org/mozilla-central/rev/7857ea04d142f2abc0d777085f9e54526c7cedf9/modules/libpref/init/StaticPrefList.yaml#8879-8883
[2] https://searchfox.org/mozilla-central/rev/7857ea04d142f2abc0d777085f9e54526c7cedf9/js/public/WasmFeatures.h#157
[3] https://searchfox.org/mozilla-central/rev/7857ea04d142f2abc0d777085f9e54526c7cedf9/js/src/wasm/WasmCompile.cpp#837
[4] https://searchfox.org/mozilla-central/rev/7857ea04d142f2abc0d777085f9e54526c7cedf9/js/src/jit/FlushICache.cpp#59

Comment 1

[Julian Seward [:jseward]]

Attachment: Bug 1957504 - wasm: enable lazy tiering for all content. r=rhunt.

Currently wasm lazy tiering is enabled by default only for content that uses
the wasm-GC feature set. This patch enables lazy tiering for all wasm content.
Lazy tiering is disallowed if the "test serialization" pref is enabled, or if
no helper threads are available.

As a ridealong fix, a potential race in CanFlushExecutionContextForAllThreads
is fixed -- applies to 32- and 64-bit ARM on Linux and Android only.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/aa847437363d
wasm: enable lazy tiering for all content.  r=rhunt.

Comment 3

[pstanciu]

Backed out for causing Mochitest LeakSanitizer failures

• Backout link
• Push with failures
• Failure Log

Comment 4

[BugBot [:suhaib / :marco/ :calixte]]

There is an r+ patch which didn't land and no activity in this bug for 2 weeks.
:jseward, could you have a look please?
If you still have some work to do, you can add an action "Plan Changes" in Phabricator.
For more information, please visit BugBot documentation.

Comment 5

[Ryan Hunt [:rhunt]]

We're working on it.

Comment 6

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/1ae7fced5a24
wasm: enable lazy tiering for all content.  r=rhunt.

Comment 7

[Atila Butkovits]

Backed out for causing failures at test_webassembly_compile.html.

Backout link: https://hg-edge.mozilla.org/integration/autoland/rev/c65e2478bd4ca1cc308428afff60c5d701f0e8d7

Push with failures: https://treeherder.mozilla.org/jobs?repo=autoland&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel&revision=1ae7fced5a24c188ab8d3ad73583161ef2f0d675&selectedTaskRun=LoIjbsxKQsSuFRq-jLkNKg.0

Failure log: https://treeherder.mozilla.org/logviewer?job_id=505907544&repo=autoland&lineNumber=5167

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/9618824194c5
wasm: enable lazy tiering for all content.  r=rhunt.

Comment 9

[Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout)]

https://hg.mozilla.org/mozilla-central/rev/9618824194c5

Comment 10

[Mayank Bansal]

17% improvement on Godot-tiering.
(this is a best guess as these tests run on m-c so i dont know how to do backfills)

Comment 11

[Mayank Bansal]

~1% overall improvement on Jetstream2
driven by:

• 41.5% improvement on hashset-runtime
• 71% on quicksort
• 15% on tsf-wasm
• 5% on richards-wasm
• 2% on gcc-loops
  probably more, but the results are noisy.

Comment 12

[Acasandrei Beatrice (needinfo me)]

(In reply to Pulsebot from comment #8)

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/9618824194c5
wasm: enable lazy tiering for all content. r=rhunt.

Perfherder has detected a devtools performance change from push 9618824194c55ecf89f162b1044e637171067a7b.

If you have any questions, please reach out to a performance sheriff. Alternatively, you can find help on Slack by joining #perf-help, and on Matrix you can find help by joining #perftest.

Improvements:

Ratio	Test	Platform	Options	Absolute values (old vs new)
17%	damp source-map.simple.DAMP	linux1804-64-shippable-qr	e10s fission stylo webrender	208.42 -> 173.52
12%	damp source-map-loader.init.DAMP	windows11-64-24h2-shippable	e10s fission stylo webrender	51.58 -> 45.37
6%	damp source-map.simple.DAMP	windows11-64-24h2-shippable	e10s fission stylo webrender	92.67 -> 87.39

Details of the alert can be found in the alert summary, including links to graphs and comparisons for each of the affected tests.

If you need the profiling jobs you can trigger them yourself from treeherder job view or ask a performance sheriff to do that for you.

You can run all of these tests on try with ./mach try perf --alert 44986

The following documentation link provides more information about this command.

Comment 13

[Florin Bilt]

(In reply to Sebastian Hengst [:aryx] (needinfo me if it's about an intermittent or backout) from comment #9)

https://hg.mozilla.org/mozilla-central/rev/9618824194c5

Perfherder has detected a mozperftest performance change from push 9618824194c55ecf89f162b1044e637171067a7b.

If you have any questions, please reach out to a performance sheriff. Alternatively, you can find help on Slack by joining #perf-help, and on Matrix you can find help by joining #perftest.

Improvements:

Ratio	Test	Platform	Options	Absolute values (old vs new)
44%	browser_translations_perf_es_en.js peak-memory-usage	windows11-64-24h2-shippable		564.99 -> 318.53
42%	browser_translations_perf_es_en.js peak-memory-usage	linux1804-64-shippable		479.39 -> 278.16
42%	browser_translations_perf_es_en.js peak-memory-usage	macosx1015-64-shippable-qr		484.70 -> 283.45
9%	browser_translations_perf_es_en.js engine-init-time	linux1804-64-shippable		299.11 -> 271.91
7%	browser_translations_perf_es_en.js stabilized-memory-usage	linux1804-64-shippable		293.92 -> 274.15
...	...	...	...	...
6%	browser_translations_perf_es_en.js stabilized-memory-usage	windows11-64-24h2-shippable		331.89 -> 311.60

Details of the alert can be found in the alert summary, including links to graphs and comparisons for each of the affected tests.

If you need the profiling jobs you can trigger them yourself from treeherder job view or ask a performance sheriff to do that for you.

You can run all of these tests on try with ./mach try perf --alert 44982

The following documentation link provides more information about this command.