runtime, cmd/trace: track goroutines blocked on GC assists
Currently when a goroutine blocks on a GC assist, it emits a generic
EvGoBlock event. Since assist blocking events and, in particular, the
length of the blocked assist queue, are important for diagnosing GC
behavior, this commit adds a new EvGoBlockGC event for blocking on a
GC assist. The trace viewer uses this event to report a "waiting on
GC" count in the "Goroutines" row. This makes sense because, unlike
other blocked goroutines, these goroutines do have work to do, so
being blocked on a GC assist is quite similar to being in the
"runnable" state, which we also report in the trace viewer.
Change-Id: Ic21a326992606b121ea3d3d00110d8d1fdc7a5ef
Reviewed-on: https://go-review.googlesource.com/30704
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
diff --git a/src/runtime/mgcmark.go b/src/runtime/mgcmark.go
index 954bbef..286aeb7 100644
--- a/src/runtime/mgcmark.go
+++ b/src/runtime/mgcmark.go
@@ -589,7 +589,7 @@
return false
}
// Park.
- goparkunlock(&work.assistQueue.lock, "GC assist wait", traceEvGoBlock, 2)
+ goparkunlock(&work.assistQueue.lock, "GC assist wait", traceEvGoBlockGC, 2)
return true
}
