Jon Coppeard (:jonco) Assignee
	Description • 6 years ago

The comments in SegmentedVector.h say:

// This class should be used in preference to mozilla::Vector or nsTArray when
// you are simply gathering items in order to later iterate over them.
//
// - In the case where you don't know the final size in advance, using
//   SegmentedVector avoids the need to repeatedly allocate increasingly large
//   buffers and copy the data into them.

This applies to our grey root buffers (Zone::gcGrayRoots_) where we gather a potentially large number of Cell pointers in the first slice of the GC so we can mark them later on.  It would be good to avoid the reallocation and copying involved with using a Vector here.

Also I'm curious what effect a different implementation would have on crashes like bug 1203273.

	Jon Coppeard (:jonco) Assignee
	Comment 1 • 5 years ago

Gray root buffering accounts for 50% of our slice overruns on beta so it's worth trying to see if we can get any improvement here:

https://telemetry.mozilla.org/new-pipeline/evo.html#!aggregates=0%2520bucket%2520percentage!49%2520bucket%2520percentage&cumulative=0&end_date=null&include_spill=0&keys=&max_channel_version=beta%252F65&measure=GC_SLOW_TASK&min_channel_version=beta%252F65&processType=*&product=Firefox&sanitize=1&sort_keys=submissions&start_date=null&trim=1&use_submission_date=0

	Paul Bone [:pbone]
	Comment 3 • 5 years ago

Comment on attachment 9037540 [details] [diff] [review]
bug1512042-gray-buffer-vector

Review of attachment 9037540 [details] [diff] [review]:
-----------------------------------------------------------------

The patch itself LGTM, but since today we're now in soft freeze.  Unless you have a strong reason to land it now (I don't know about Bug 1203273)
then maybe wait until next week.

	Pulsebot
	Comment 4 • 5 years ago

Pushed by jcoppeard@mozilla.com:
https://hg.mozilla.org/integration/mozilla-inbound/rev/4ac26510b88f
Try using SegmentedVector for gray root buffers r=pbone

	Pulsebot
	Comment 5 • 5 years ago

Pushed by jcoppeard@mozilla.com:
https://hg.mozilla.org/integration/mozilla-inbound/rev/231f059ad9d9
Fix bustage on MacOS X r=me on a CLOSED TREE