1661339 - Run the background tasks for gathering printer capabilities on the IO thread pool

Status: RESOLVED FIXED

(Core :: Printing: Setup, defect, P1)

Description

[Jonathan Watt [:jwatt]]

Bob has discovered while adding telemetry that sometimes the entire roundtrip from the main thread to the background task thread and back again is taking substantially longer than the time to make the blocking calls on the background thread.

I asked about whether we can somehow give the tasks a higher priority in the #xpcom Matrix channel. However, unfortunately background tasks can't currently be given a priority. :-( Creating our own dedicated thread [pool] is also only something to consider as a last resort.

One thing that we noticed is that we're failing to pass NS_DISPATCH_EVENT_MAY_BLOCK when calling NS_DispatchBackgroundTask, which we're required to do for blocking tasks. Passing that will make the tasks run on the IO pool, and kriswright tells me that since that poll has more threads we may get better responsiveness.

Comment 1

[Jonathan Watt [:jwatt]]

Attachment: Bug 1661339. Run the background tasks for gathering printer capabilities on the IO thread pool. r=emilio

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/3bd84146cbf6
Run the background tasks for gathering printer capabilities on the IO thread pool. r=emilio

Comment 3

[Cristina Coroiu [:ccoroiu]]

https://hg.mozilla.org/mozilla-central/rev/3bd84146cbf6

Comment 4

[Jonathan Watt [:jwatt]]

Comment on attachment 9172252 [details]
Bug 1661339. Run the background tasks for gathering printer capabilities on the IO thread pool. r=emilio

Beta/Release Uplift Approval Request

• User impact if declined: Potential jankiness due to running blocking tasks on the wrong thread pool.
• Is this code covered by automated tests?: No
• Has the fix been verified in Nightly?: Yes
• Needs manual test from QE?: No
• If yes, steps to reproduce:
• List of other uplifts needed: None
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): Just switching background task thread pool to the correct pool.
• String changes made/needed:

Comment 5

[Julien Cristau [:jcristau] (back April 22)]

Comment on attachment 9172252 [details]
Bug 1661339. Run the background tasks for gathering printer capabilities on the IO thread pool. r=emilio

approved for 81.0b3

Comment 6

[Julien Cristau [:jcristau] (back April 22)]

https://hg.mozilla.org/releases/mozilla-beta/rev/1756ee216832