Closed Bug 1754764 Opened 3 years ago Closed 2 years ago

1.38 - 1.35% Base Content JS / Base Content JS + 2 more (Linux, OSX, Windows) regression on Tue February 8 2022


(Core :: JavaScript Engine: JIT, defect, P3)

Firefox 99



Tracking Status
firefox-esr91 --- unaffected
firefox97 --- unaffected
firefox98 --- unaffected
firefox99 --- affected


(Reporter: aglavic, Unassigned)


(Blocks 1 open bug, Regression)


(Keywords: perf, perf-alert, regression)

Perfherder has detected a awsy performance regression from push 250fa587c2b0099be744469c3ff60fc4e8e79092. As author of one of the patches included in that push, we need your help to address this regression.


Ratio Test Platform Options Absolute values (old vs new)
1% Base Content JS linux1804-64-shippable-qr 1,785,236.67 -> 1,809,832.00
1% Base Content JS windows10-64-2004-shippable-qr 1,786,520.00 -> 1,811,192.00
1% Base Content JS macosx1015-64-shippable-qr 1,813,912.00 -> 1,838,488.00
1% Base Content JS macosx1015-64-shippable-qr 1,813,912.00 -> 1,838,488.00

Details of the alert can be found in the alert summary, including links to graphs and comparisons for each of the affected tests. Please follow our guide to handling regression bugs and let us know your plans within 3 business days, or the offending patch(es) will be backed out in accordance with our regression policy.

For more information on performance sheriffing please see our FAQ.

Flags: needinfo?(jdemooij)

Set release status flags based on info from the regressing bug 1753633

Has Regression Range: --- → yes

This is a typical performance vs memory trade-off unfortunately, I think we'll have to accept this one. We could shrink the cache but that makes it a lot less effective. Another option is lazy initialization and destroying the cache on GC, but that would add more branches and a level of indirection.

Flags: needinfo?(jdemooij)
Priority: -- → P3

Closing per comment 2.

Closed: 2 years ago
Resolution: --- → WORKSFORME
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