1635678 - 3.2 - 3.68% Heap Unclassified (windows10-64-shippable) regression on push 5f1618cc19f5d34eedb2dc62dd64043b62af4e48 (Fri May 1 2020)

Status: RESOLVED FIXED

(Core :: DOM: CSS Object Model, defect)

Description

[Marian Raiciof [:marauder]]

Perfherder has detected a awsy performance regression from push 5f1618cc19f5d34eedb2dc62dd64043b62af4e48. As author of one of the patches included in that push, we need your help to address this regression.

Regressions:

4% Heap Unclassified windows10-64-shippable opt 50,035,948.69 -> 51,877,529.43
3% Heap Unclassified windows10-64-shippable opt 50,046,108.22 -> 51,767,165.13
3% Heap Unclassified windows10-64-shippable opt tp6 68,458,190.91 -> 70,646,151.29

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.

Comment 1

[Erik Nordin [:nordzilla]]

[Bug 1632686] introduced behavior where StyleSheets are cloned before they are put into the XUL cache [here].

It's understandable that this would cause more overall heap allocations. I am looking into whether memory reporting the XUL cache will improve these numbers in [Bug 1636266].

I find it curious that the alert was triggered only for Windows10-64.

Comment 2

[Erik Nordin [:nordzilla]]

It looks like adding memory reporting to the StyleSheets in the XUL cache in [Bug 1636266] will re-classify this unclassified memory, based on these comparisons:

https://treeherder.mozilla.org/perf.html#/compare?originalProject=try&originalRevision=80c975e1b1a430686d0a9ae71285bfb65e224abb&newProject=try&newRevision=a2a12252705d9ca8e89cdf2a12a21a2896c8857c&framework=4

I expect that this regression will be fixed once that patch lands.

Comment 3

[Erik Nordin [:nordzilla]]

The patch has landed.

marauder, can you double check that you are no longer seeing this issue?

Comment 4

[Marian Raiciof [:marauder]]

Thanks Erik, yes all good!

https://treeherder.mozilla.org/perf.html#/graphs?highlightAlerts=1&series=autoland,1959177,1,4&timerange=1209600&zoom=1588285671705,1589075968055,48680760.292383924,55272111.36125706