1723813 - Add a profiler marker in nsSocketTransportService::Poll

Status: RESOLVED FIXED

(Core :: Networking, task, P2)

Description

[Florian Quèze [:florian]]

This will be helpful to understand bug 1709175, and should remain generally useful afterwards.

Comment 1

[Florian Quèze [:florian]]

Attachment: Bug 1723813 - Add a profiler marker in nsSocketTransportService::Poll to help understand excessive CPU use on the Socket Thread, r=mstange.

Comment 2

[Florian Quèze [:florian]]

Example profile: https://share.firefox.dev/3A6z7zP

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/fb900d90b4c9
Add a profiler marker in nsSocketTransportService::Poll to help understand excessive CPU use on the Socket Thread, r=mstange,necko-reviewers,valentin,gerald.

Comment 4

[Narcis Beleuzu [:NarcisB]]

https://hg.mozilla.org/mozilla-central/rev/fb900d90b4c9

Comment 5

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

This marker is super-high volume; on a profile of fast.net, I see 30% of the CPU time used in the transfer by socketthread going to the printfcstring() calls. (~10-15% of a core). And they're all basically identical.

Perhaps this should be optional via ifdef or profiler feature. i don't think this is generally useful in enough cases to leave it in, as it affects real performance when trying to do large transfers

https://share.firefox.dev/42OOMU2

Comment 6

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

perhaps we should put this behind an:
#if defined(DEBUG) || defined (POLL_MARKERS)
which would avoid it bitrotting, but also avoid it interfering with profiles except when we want to actively investigate poll issues.

Comment 7

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

Profile with it #defined out: https://share.firefox.dev/3SKnAkK
CPU use is ~10%+ lower during transfer (and transfer was a bit higher, ~950-980Mbps, though that is likely not due to the change, but it should have pushed CPU even a bit higher)

Comment 8

[Florian Quèze [:florian]]

(In reply to Randell Jesup [:jesup] (needinfo me) from comment #7)

Profile with it #defined out: https://share.firefox.dev/3SKnAkK

What happened to the Awake markers in the socket thread of the parent in that profile? https://share.firefox.dev/4bP50R3 They seem to finish but never start.

Comment 9

[Florian Quèze [:florian]]

(In reply to Randell Jesup [:jesup] (needinfo me) from comment #5)

This marker is super-high volume; on a profile of fast.net, I see 30% of the CPU time used in the transfer by socketthread going to the printfcstring() calls. (~10-15% of a core). And they're all basically identical.

I see only 12 samples in nsPrintfCString::nsPrintfCString, how do you get to that 30% figure?