963844 - Run ICC more aggressively when there's a lot of activity

Status: RESOLVED FIXED

(Core :: XPCOM, defect)

Description

[Andrew McCreight [:mccr8]]

I think this is needed to avoid getting timeouts on Mochitest-BC.

One thing I've tried out which seems to work fairly well in local testing is to scale the slice budget by the % amount we've fallen behind our target for scheduling slices.  For example, we try to run 10ms slices every 32ms.  If we end up spending 64ms between two slices instead, then we'll budget 20ms of ICC work.  That way we're doing a roughly constant amount of CC work per unit of wall clock time.

Comment 1

[Andrew McCreight [:mccr8]]

Attachment: Scale ICC budget by time between slices

https://tbpl.mozilla.org/?tree=Try&rev=7d9d488db089

Comment 2

[Andrew McCreight [:mccr8]]

Well, with that, it is only failing 50% of the time, and both failures are on a single test, so that's an improvement.

Comment 3

[Andrew McCreight [:mccr8]]

Attachment: Scale ICC budget by time between slices. r=smaug

If we exceed the desired length of time between ICC slices, proportionally scale up the slice budget to try to ensure a constant amount of collection work is done per unit of time, even when the browser is under heavy load.

As part of this, track the time the last slice from the current ICC ended.

https://tbpl.mozilla.org/?tree=Try&rev=1e1b69edc562

Comment 4

[Andrew McCreight [:mccr8]]

Earlier, I had some kind of threshold for the scaling factor, and if you fell below that threshold, you'd just do the regular slice time, but that seems overly complex at this point.  Maybe later it will be worthwhile doing that kind of tuning.

Comment 5

[Olli Pettay [:smaug][[e-mail]]]

Comment on attachment 8385735 [details] [diff] [review]
Scale ICC budget by time between slices. r=smaug

Rename ICCSliceTime to
CollectCycleCollectionSlice or some such and
call nsCycleCollector_collectSlice inside that method using the
value you get using the algorithm in this patch?
I think the patch as such is a bit too confusing - at least to understand
at 3:30am.

Comment 6

[Andrew McCreight [:mccr8]]

Attachment: Scale ICC budget by time between slices.

Comment 7

[Olli Pettay [:smaug][[e-mail]]]

Comment on attachment 8386881 [details] [diff] [review]
Scale ICC budget by time between slices.


>+      // Only run a limited slice if we're within the max running time.
>+      if (TimeBetween(gCCStats.mBeginTime, now) < kMaxICCDuration) {
>+        float sliceMultiplier = TimeBetween(gCCStats.mEndSliceTime, now) / kICCIntersliceDelay;
Can you add some max(sliceMultiplier, 1) thing here.

Comment 8

[Andrew McCreight [:mccr8]]

Added max.  Thanks for all of your feedback.

https://hg.mozilla.org/integration/mozilla-inbound/rev/de9636679191

Comment 9

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/de9636679191