1689698 - Intermediate preloading uses 40% CPU for over 10 seconds

Status: RESOLVED FIXED

(Core :: Security: PSM, defect)

Description

[Markus Stange [:mstange]]

Profile: https://share.firefox.dev/3iYA5Xs
(originally from bug 1679506 comment 2)

This profile shows many many requests to .pem files, over the span of at least 10 seconds, with about 40% CPU usage, on the main thread. That seems a little high.

Is there something we can do to reduce this? Could the files be combined into bigger "chunk" files? Could the parsing be sped up?

Comment 1

[Dana Keeler (she/her) (use needinfo) [:keeler] (on leave)]

Attachment: Bug 1689698 - improve performance of DER.jsm r?mbirghan

This patch improves the performance of DER.jsm by changing readBytes to use
slice rather than repeatedly calling readByte.
Additionally, this patch removes the validation that the input to DERDecoder
consists of an array of integers in the range [0, 255]. This check is
unnecessary for all current consumers of DER.jsm because the input comes from
atob, which only outputs values in that range. If other consumers use DER.jsm
in the future, they will have to determine whether or not they need to validate
the input themselves first.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/eb3ee8b2a4d7
improve performance of DER.jsm r=mbirghan

Comment 3

[Atila Butkovits]

https://hg.mozilla.org/mozilla-central/rev/eb3ee8b2a4d7

Comment 4

[Dana Keeler (she/her) (use needinfo) [:keeler] (on leave)]

Has this improved things? My measurements indicated this would reduce the work done by 60-70%, but I didn't directly measure the work originally measured in comment 0.

Comment 5

[Markus Stange [:mstange]]

I'm not sure how to exercise this code. The profile I saw this in was obtained by a QA person investigating a different issue, and the preloading only happened by accident during the profiled window. Is there a way I can manually trigger this?

Comment 6

[Dana Keeler (she/her) (use needinfo) [:keeler] (on leave)]

(In reply to Markus Stange [:mstange] from comment #5)

I'm not sure how to exercise this code. The profile I saw this in was obtained by a QA person investigating a different issue, and the preloading only happened by accident during the profiled window. Is there a way I can manually trigger this?

Maybe we could ask the QA person? 😅
This code generally only gets run once, to download all known intermediate certificates. It's on an idle timer, so I suppose you could create a new profile, start the profiler, and let the browser sit for a bit?