1965398 - Testcase preloading and then querying cache is 4.5x slower in Firefox compared to Chrome

Status: NEW

(Core :: Networking, defect, P3)

Description

[Mayank Bansal]

Attachment: cache test first network then cache only.HTML

Serve the testcase over a simple HTTP server
Open the testcase
Input 50000 and click on run

Firefox gecko profiler: https://share.firefox.dev/433pbHp (40s)
Firefox samply profiler: https://share.firefox.dev/3Sq879I (38s)
Chrome samply: https://share.firefox.dev/4iV48wK (9s)

Comment 1

[Mayank Bansal]

Attachment: about:support

Comment 2

[Randell Jesup [:jesup] (needinfo me)]

Note that UBlock seems heavily involved; can you retake the profiles without ublock? https://share.firefox.dev/42QIXqS
Also, collect the profile with the Networking preset if you can. Thanks!

Comment 3

[Mayank Bansal]

Fresh profile, no addons. Networking preset logging.
N=10k. (Profile with N=50k is too big to capture)
https://share.firefox.dev/4jTvQLJ (13s)

Comment 4

[Mayank Bansal]

With this test (and another 1-2 for which i didnt file bugs), i am trying to test the performance of the cache of browsers. The idea being that people visit the same set of websites. So the perf of reading/validating existing data from the cache should be fast.

Comment 5

[Randell Jesup [:jesup] (needinfo me)]

FYI. The profile shows that the cache appears to be uninvolved; the issue is the CPU needed to create a channel, and the biggest culprit appears to be the Classifier.

Comment 6

[Randell Jesup [:jesup] (needinfo me)]

To elaborate: over 70% of the CPU time seems to be taken by channel creation, and the largest single runnable of that is ~31% in the Classifier - return runnable (which kicks off the next/primary stage of channel creation). "Task AsyncUrlChannelClassifier::CheckChannel - return" in https://share.firefox.dev/46nAtt3

26% Task PNecko::Msg_PHttpChannelConstructor
13% HttpChannelParent::TryInvokeAsyncOpen
and others

Jeff points out that markers are using up a lot of CPU here too.