87% regression in ss-dna on ARM

RESOLVED WORKSFORME

Status

()

Core
JavaScript Engine: JIT
RESOLVED WORKSFORME
4 years ago
3 years ago

People

(Reporter: h4writer, Unassigned)

Tracking

unspecified
ARM
All
Points:
---

Firefox Tracking Flags

(firefox33 affected, firefox34 affected, b2g-v2.0 affected, b2g-v2.1 affected)

Details

(Reporter)

Description

4 years ago
AWFY is reporting a 87% regression in ss-dna on

- ARMv7 (odroid-xu, hf, shell)
http://arewefastyet.com/#machine=20&view=single&suite=ss&subtest=dna&start=1411396565&end=1411517425

- ARMv7 (pandboard-es, hf, shell)
http://arewefastyet.com/#machine=21&view=single&suite=ss&subtest=dna&start=1411396565&end=1411517425

The regression range is:
http://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=d353d79e0610&tochange=db6a403deb38

My eye catched "Bug 1013996 - irregexp: Avoid unaligned accesses in ARM code. r=bhackett" which is the only ARM-only change. So I think that caused it.
(Reporter)

Updated

4 years ago
Depends on: 1013996
Flags: needinfo?(dtc-moz)
status-b2g-v2.0: --- → affected
status-b2g-v2.1: --- → affected
status-firefox33: --- → affected
status-firefox34: --- → affected
(In reply to Hannes Verschore [:h4writer] from comment #0)
> AWFY is reporting a 87% regression in ss-dna on
...
> My eye catched "Bug 1013996 - irregexp: Avoid unaligned accesses in ARM
> code. r=bhackett" which is the only ARM-only change. So I think that caused
> it.

Some regression was expected here, but I am surprise by the magnitude. However it does not appear to affect all regexp benchmarks. Release 32 also had this optimization disabled and there are no plans to fix this in 33, or 34. The fix is to dynamically test if the device has alignment checks enabled. We have no devices to test this so it will have some risk and should ride the train. It might make 35.
Flags: needinfo?(dtc-moz)

Comment 3

4 years ago
Something inside this range (http://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=795d9067f6c6&tochange=1b532d05bccf) fixed this regression.

Updated

3 years ago
Status: NEW → RESOLVED
Last Resolved: 3 years ago
Resolution: --- → WORKSFORME
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