runtime: remove pointless harvestwbufs

Currently we harvestwbufs the moment we enter the mark phase, even
before starting the world again. Since cached wbufs are only filled
when we're in mark or mark termination, they should all be empty at
this point, making the harvest pointless. Remove the harvest.

We should, but do not currently harvest at the end of the mark phase
when we're running out of work to do.

Change-Id: I5f4ba874f14dd915b8dfbc4ee5bb526eecc2c0b4
Reviewed-on: https://go-review.googlesource.com/7669
Reviewed-by: Rick Hudson <rlh@golang.org>

diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index 541dbc615dbbd16956d06b7a525afc7408210d0c..0b15a8500d2d30c3062525af25d4caa00aca9409 100644 (file)
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -336,7 +336,6 @@ func gc(mode int) {
                        // Sync.
                        stoptheworld()
                        gcphase = _GCmark
-                       harvestwbufs()
 
                        // Concurrent mark.
                        starttheworld()