From 78a1064d5dd05fc669342df3a6a5e11d49749d85 Mon Sep 17 00:00:00 2001 From: Matthew Dempsky Date: Mon, 27 Jul 2020 14:05:05 -0700 Subject: [PATCH] runtime: remove scase.releasetime field selectgo will report at most one block event, so there's no need to keep a releasetime for every select case. It suffices to simply track the releasetime of the case responsible for the wakeup. Updates #40410. Change-Id: I72679cd43dde80d7e6dbab21a78952a4372d1e79 Reviewed-on: https://go-review.googlesource.com/c/go/+/245122 Run-TryBot: Matthew Dempsky TryBot-Result: Gobot Gobot Reviewed-by: Keith Randall --- src/cmd/compile/internal/gc/select.go | 1 - src/runtime/select.go | 23 ++++++++++------------- 2 files changed, 10 insertions(+), 14 deletions(-) diff --git a/src/cmd/compile/internal/gc/select.go b/src/cmd/compile/internal/gc/select.go index 49cc23cd3d..eb5ff8469b 100644 --- a/src/cmd/compile/internal/gc/select.go +++ b/src/cmd/compile/internal/gc/select.go @@ -386,7 +386,6 @@ func scasetype() *types.Type { namedfield("elem", types.Types[TUNSAFEPTR]), namedfield("kind", types.Types[TUINT16]), namedfield("pc", types.Types[TUINTPTR]), - namedfield("releasetime", types.Types[TINT64]), }) scase.SetNoalg(true) } diff --git a/src/runtime/select.go b/src/runtime/select.go index 081db7bad4..2f8b139155 100644 --- a/src/runtime/select.go +++ b/src/runtime/select.go @@ -26,11 +26,10 @@ const ( // Known to compiler. // Changes here must also be made in src/cmd/internal/gc/select.go's scasetype. type scase struct { - c *hchan // chan - elem unsafe.Pointer // data element - kind uint16 - pc uintptr // race pc (for race detector / msan) - releasetime int64 + c *hchan // chan + elem unsafe.Pointer // data element + kind uint16 + pc uintptr // race pc (for race detector / msan) } var ( @@ -142,9 +141,6 @@ func selectgo(cas0 *scase, order0 *uint16, ncases int) (int, bool) { var t0 int64 if blockprofilerate > 0 { t0 = cputicks() - for i := 0; i < ncases; i++ { - scases[i].releasetime = -1 - } } // The compiler rewrites selects that statically have @@ -227,6 +223,7 @@ func selectgo(cas0 *scase, order0 *uint16, ncases int) (int, bool) { var casi int var cas *scase var caseSuccess bool + var caseReleaseTime int64 = -1 var recvOK bool for i := 0; i < ncases; i++ { casi = int(pollorder[i]) @@ -346,14 +343,14 @@ func selectgo(cas0 *scase, order0 *uint16, ncases int) (int, bool) { if k.kind == caseNil { continue } - if sglist.releasetime > 0 { - k.releasetime = sglist.releasetime - } if sg == sglist { // sg has already been dequeued by the G that woke us up. casi = int(casei) cas = k caseSuccess = sglist.success + if sglist.releasetime > 0 { + caseReleaseTime = sglist.releasetime + } } else { c = k.c if k.kind == caseSend { @@ -483,8 +480,8 @@ send: goto retc retc: - if cas.releasetime > 0 { - blockevent(cas.releasetime-t0, 1) + if caseReleaseTime > 0 { + blockevent(caseReleaseTime-t0, 1) } return casi, recvOK -- 2.50.0