From 640cd3b3220f7a06820365e53f8fc6cb0acd1b20 Mon Sep 17 00:00:00 2001 From: Austin Clements Date: Thu, 23 Feb 2017 11:04:37 -0500 Subject: [PATCH] runtime: check transition condition before triggering periodic GC Currently sysmon triggers periodic GC if GC is not currently running and it's been long enough since the last GC. This misses some important conditions; for example, whether GC is enabled at all by GOGC. As a result, if GOGC is off, once we pass the timeout for periodic GC, sysmon will attempt to trigger a GC every 10ms. This GC will be a no-op because gcStart will check all of the appropriate conditions and do nothing, but it still goes through the motions of waking the forcegc goroutine and printing a gctrace line. Fix this by making sysmon call gcShouldStart to check *all* of the appropriate transition conditions before attempting to trigger a periodic GC. Fixes #19247. Change-Id: Icee5521ce175e8419f934723849853d53773af31 Reviewed-on: https://go-review.googlesource.com/37515 Run-TryBot: Austin Clements TryBot-Result: Gobot Gobot Reviewed-by: Rick Hudson --- src/runtime/proc.go | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/src/runtime/proc.go b/src/runtime/proc.go index 8dede3fb23..ae19120a31 100644 --- a/src/runtime/proc.go +++ b/src/runtime/proc.go @@ -3791,7 +3791,7 @@ func sysmon() { } // check if we need to force a GC lastgc := int64(atomic.Load64(&memstats.last_gc_nanotime)) - if gcphase == _GCoff && lastgc != 0 && now-lastgc > forcegcperiod && atomic.Load(&forcegc.idle) != 0 { + if gcShouldStart(true) && lastgc != 0 && now-lastgc > forcegcperiod && atomic.Load(&forcegc.idle) != 0 { lock(&forcegc.lock) forcegc.idle = 0 forcegc.g.schedlink = 0