From f10d99f51da73721dd0b9ab1c03c4a868a991756 Mon Sep 17 00:00:00 2001 From: Austin Clements Date: Fri, 1 Jul 2016 11:31:04 -0400 Subject: [PATCH] runtime: flush assist credit on goroutine exit Currently dead goroutines retain their assist credit. This credit can be used if the goroutine gets recycled, but in general this can make assist pacing over-aggressive by hiding an amount of credit proportional to the number of exited (and not reused) goroutines. Fix this "hidden credit" by flushing assist credit to the global credit pool when a goroutine exits. Updates #14812. Change-Id: I65f7f75907ab6395c04aacea2c97aea963b60344 Reviewed-on: https://go-review.googlesource.com/24703 Run-TryBot: Austin Clements TryBot-Result: Gobot Gobot Reviewed-by: Rick Hudson --- src/runtime/proc.go | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/src/runtime/proc.go b/src/runtime/proc.go index 8adf3b2725..02c092711c 100644 --- a/src/runtime/proc.go +++ b/src/runtime/proc.go @@ -2671,6 +2671,15 @@ func goexit0(gp *g) { gp.labels = nil gp.timer = nil + if gcBlackenEnabled != 0 && gp.gcAssistBytes > 0 { + // Flush assist credit to the global pool. This gives + // better information to pacing if the application is + // rapidly creating an exiting goroutines. + scanCredit := int64(gcController.assistWorkPerByte * float64(gp.gcAssistBytes)) + atomic.Xaddint64(&gcController.bgScanCredit, scanCredit) + gp.gcAssistBytes = 0 + } + // Note that gp's stack scan is now "valid" because it has no // stack. gp.gcscanvalid = true