1843538 - vixl::<ID_REG>::GetCpuFeatures() is slow on some Android devices

Status: RESOLVED FIXED

(Core :: Performance, defect)

Description

[Jamie Nicol [:jnicol]]

https://share.firefox.dev/3XUGIyO

This shows up in speedometer profiles during baseline compilation. However, it only shows up on certain devices: eg Pixel 4, Pixel 5, Pixel 6, Pixel 7. Samsung S10, Samsung S20, Samsung A51. From the devices I've tested it appears to affect all devices running a kernel version >= 4.14, and affects no devices running an earlier kernel, though my sample size is fairly small.

Perhaps we can cache the features somewhere rather than querying them for every compilation.

Comment 1

[Benjamin De Kosnik [:bdekoz]]

Set priority as low according to perf impact calc, but obviously we care about speedometer

Comment 2

[Jamie Nicol [:jnicol]]

Attachment: Bug 1843538 - Query AARCH64 CPU features once and cache result

On android devices repeatedly querying the CPU's features can be
expensive and frequently shows up in speedometer profiles. This patch
makes us query the features the first time they are required, then on
subsequent occaisions we reuse the cached result instead of querying
again each time.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/5b2ef63ae58e
Query AARCH64 CPU features once and cache result r=jseward

Comment 4

[Cristian Tuns]

https://hg.mozilla.org/mozilla-central/rev/5b2ef63ae58e