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internal/trace: stable sort events

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On some VMs two events can happen at the same time. For examples:
179827399 GoStart p=2 g=11 off=936359 g=11
179827399 GoUnblock p=2 g=0 off=936355 g=11
If we do non-stable sort, the events can be reordered making the trace inconsistent.
Do stable sort instead.

Batches are dumped in FIFO order, so if these same-time events are split into
separate batches, stable sort still works.

Events on different CPUs go into different batches and can be reordered.
But the intention is that causally-related events on different CPUs
will have larger (non-zero) time diff.

Update #11320

Change-Id: Id1df96af41dff68ea1782ab4b23d5afd63b890c9
Reviewed-on: https://go-review.googlesource.com/11834
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Dmitry Vyukov 2015-07-01 16:41:27 +02:00 committed by Brad Fitzpatrick
parent cd2e2f60e7
commit 64e48bbaba
1 changed files with 1 additions and 1 deletions
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2
src/internal/trace/parser.go
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@ -254,7 +254,7 @@ func parseEvents(rawEvents []rawEvent) (events []*Event, err error) {
}
// Sort by time and translate cpu ticks to real time.
sort.Sort(eventList(events))
sort.Stable(eventList(events))
if ticksPerSec == 0 {
err = fmt.Errorf("no EvFrequency event")
return