1372851 - Disable TraceLogger by default in opt builds

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, defect)

Description

[Jan de Mooij [:jandem]]

Attachment: Patch

Baseline can emit TraceLogger instrumentation for entering/exiting a script, and just emitting this code can be pretty slow. In profiles it's often like 10% of Baseline compilation time for small scripts, because we have to push/pop all volatile registers etc. Furthermore, at runtime we jump over this code if TL is disabled, but it's quite a big chunk of JIT code so it still pollutes the instruction cache for no good reason.

We have seen TL overhead before and it's hard to justify considering only a handful of SpiderMonkey hackers use it.

The attached patch disables TL by default in opt builds. It's still enabled in debug builds (to catch obvious build issues) and it can be enabled in opt builds with --enable-trace-logging.

Comment 1

[Benjamin Bouvier [:bbouvier] (inactive)]

Comment on attachment 8877515 [details] [diff] [review]
Patch

Review of attachment 8877515 [details] [diff] [review]:
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Sounds good to me, thanks for the patch.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/mozilla-inbound/rev/401475243963
Disable TraceLogger by default in opt builds. r=bbouvier

Comment 3

[Jan de Mooij [:jandem]]

This improved a bunch of shell benchmarks on AWFY: a few % on Sunspider, Octane-CodeLoad, and also some pretty big improvements on some six-speed tests.

Comment 4

[Joel Maher ( :jmaher ) (UTC -8)]

a perf improvement:
== Change summary for alert #7286 (as of June 14 2017 11:04 UTC) ==

Improvements:

  3%  quantum_pageload_facebook summary windows7-32 opt e10s     1,436.17 -> 1,389.96

For up to date results, see: https://treeherder.mozilla.org/perf.html#/alerts?id=7286

Comment 5

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

https://hg.mozilla.org/mozilla-central/rev/401475243963