1587785 - Disable background hang monitor for raptor tests

Status: RESOLVED FIXED

(Testing :: Raptor, task, P1)

Comment 1

[Robert Wood [:rwood]]

Hi :jesup, :florian, is there a browser pref that I can use to turn this off? Thanks!

Comment 2

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

pref("toolkit.content-background-hang-monitor.disabled", false);

However, people have commented that this merely disables the reporting and you have to compile it out, and I've verified it starts BHMgr Monitor and BHMgr Processor threads even with the thread flipped. That needs to be fixed.

The DisableOnBeta() function calls BHM::Shutdown() on Master Process and sets sDisabled=true on content processes; however nothing stops it from starting BackgroundHangThread on Nightly -- and if I read this right (BackgroundHangMonitor::Startup()) it starts the BHM thread on any non-beta channel for master process (but not content processes). And I see BHM active in the Master process even with the pref flipped: https://perfht.ml/3261Zry

Note that BHMgr Monitor appears to not be an nsThread, and so the profiler can't capture it

However:

It was enabled for 1% of the beta population 5 years ago, then expanded to 100% of beta, it was turned off for beta 2 years ago (well, virtually turned off - userid? MOD INT32_MAX) in bug 1380081. It seems to be build-disabled in everything but Nightly now (via moz.build).

Comment 3

[Florian Quèze [:florian]]

(In reply to Randell Jesup [:jesup] (needinfo me) from comment #2)

pref("toolkit.content-background-hang-monitor.disabled", false);

I had a quick look at the code and was under the impression that this pref is meant to disable BHR only for content processes. I don't think we currently have a pref that can completely turn it off.

To disable it for our performance test infrastructure, I wonder if the best way could be an environment variable. Either a new one that we could add in the BHR code and in the test harness, or an existing one already set by the test harness that we would start checking in the BHR code.

Comment 4

[Vicky Chin [:vchin]]

Randell, can you provide more background info on the overhead from BHR and how it may impact test results?

Comment 5

[Robert Wood [:rwood]]

Hey all is there a consensus here on how this should cam be disabled? If it's just a matter of setting an environment variable in the production environment please just let me know and I can easily make that update, thanks!

Comment 6

[Andrew Creskey [:acreskey]]

The BHR can be disabled in content processes by setting this pref:
toolkit.content-background-hang-monitor.disabled to true
See Bug 1530617. There is currently no method to completely disable the BHR on Nightly.
With this pref set, I haven't personally seen BHR keeping any threads busy for long periods of time.

Comment 7

[Robert Wood [:rwood]]

Attachment: Bug 1587785 - Disable background hang monitor for raptor tests

Comment 8

[Robert Wood [:rwood]]

https://treeherder.mozilla.org/#/jobs?repo=try&revision=c30b494568060a96df57b85f4c51be1b4eef4ec1

Comment 9

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/dbbb3860dd3e
Disable background hang monitor for raptor tests r=acreskey,stephendonner

Comment 10

[Daniel Varga [:dvarga]]

https://hg.mozilla.org/mozilla-central/rev/dbbb3860dd3e