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runtime: run concurrent mark phase on regular stack

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Currently, the GC's concurrent mark phase runs on the system
stack. There's no need to do this, and running it this way ties up the
entire M and P running the GC by preventing the scheduler from
preempting the GC even during concurrent mark.

Fix this by running concurrent mark on the regular G stack. It's still
non-preemptible because we also set preemptoff around the whole GC
process, but this moves us closer to making it preemptible.

Change-Id: Ia9f1245e299b8c5c513a4b1e3ef13eaa35ac5e73
Reviewed-on: https://go-review.googlesource.com/7730
Reviewed-by: Rick Hudson <rlh@golang.org>
This commit is contained in:
Austin Clements 2015-03-18 11:22:12 -04:00
parent bef356b282
commit fa2f9c2c09
1 changed files with 11 additions and 11 deletions
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22
src/runtime/mgc.go
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@ -339,18 +339,18 @@ func gc(mode int) {
// Concurrent mark.
starttheworld()
gctimer.cycle.mark = nanotime()
var gcw gcWork
gcDrain(&gcw)
gcw.dispose()
// Begin mark termination.
gctimer.cycle.markterm = nanotime()
stoptheworld()
// The gcphase is _GCmark, it will transition to _GCmarktermination
// below. The important thing is that the wb remains active until
// all marking is complete. This includes writes made by the GC.
})
gctimer.cycle.mark = nanotime()
var gcw gcWork
gcDrain(&gcw)
gcw.dispose()
// Begin mark termination.
gctimer.cycle.markterm = nanotime()
systemstack(stoptheworld)
// The gcphase is _GCmark, it will transition to _GCmarktermination
// below. The important thing is that the wb remains active until
// all marking is complete. This includes writes made by the GC.
} else {
// For non-concurrent GC (mode != gcBackgroundMode)
// The g stacks have not been scanned so clear g state