1088293 - Dromaeo Object String is a lot slower with PGO

Status: RESOLVED WONTFIX

(Core :: JavaScript Engine: JIT, defect, P5)

Description

[Guilherme Lima]

According to http://arewefastyet.com/#machine=17&view=single&suite=dromaeo&subtest=dromaeo-object-string Nightly with PGO is 60% slower than without.
The last 2 patches from bug 1074961 cut 1/3 from the distance (but were backed out).
All the other tests from Dromaeo perform better or at the same level with PGO.

Comment 1

[Guilherme Lima]

I don't know how, but something in this range improved a lot the PGO version: http://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=19beeeec9cf3&tochange=927503f08f55
PGO is now only ~5% slower than without.

Comment 2

[Jan de Mooij [:jandem]]

AWFY shows this is bimodal now:

http://arewefastyet.com/#machine=17&view=single&suite=dromaeo&subtest=dromaeo-object-string

Some runs are fast, others are slow... The non-PGO build doesn't have this issue; might be a timing/GC thing in the profile run? :(

I'll clear the needinfo; it's not super urgent and I'm drowning in needinfo/review requests atm.

Comment 3

[Jon Coppeard (:jonco)]

I checked AWFY again and this is still bimodal, with PGO builds sometimes ~50% slower.

Comment 4

[Mayank Bansal]

PGO has been the default for a long time, and Dromaeo is no longer the most relavent benchmark. Closing this.