1746263 - Shortly after startup, load_crlite_stash_from_reader_into_map uses 160ms+ of CPU time calling read()

Status: RESOLVED FIXED

(Core :: Security: PSM, defect)

Description

[Markus Stange [:mstange]]

I found a fun issue while doing startup profiling, and it has an easy fix.

Profile: https://share.firefox.dev/3GNKtMs

Steps to reproduce:

1. Start Firefox with the environment variables MOZ_PROFILER_STARTUP=1 MOZ_PROFILER_STARTUP_FILTERS="GeckoMain,Background"
2. Grab a profile.
3. Look at the activity on the BackgroundThreadPool threads.

Expected results:
No avoidable activity.

Actual results:
More than 160ms of CPU time are spent in load_crlite_stash_from_reader_into_map, and most of that inside of a read system call. See the profile at the top of this comment.

Comment 1

[Markus Stange [:mstange]]

Attachment: Bug 1746263 - Use BufReader when reading the crlite stash. r=keeler

This saves at least 140ms of CPU time during startup from repeated read calls.

Comment 2

[Markus Stange [:mstange]]

Profile with fix: https://share.firefox.dev/3GHaH36

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/c839cbc79a12
Use BufReader when reading the crlite stash. r=keeler

Comment 4

[Cristian Tuns]

https://hg.mozilla.org/mozilla-central/rev/c839cbc79a12