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 <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
diff --git a/src/cmd/compile/internal/gc/select.go b/src/cmd/compile/internal/gc/select.go
index 49cc23c..eb5ff84 100644
--- a/src/cmd/compile/internal/gc/select.go
+++ b/src/cmd/compile/internal/gc/select.go
@@ -386,7 +386,6 @@
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 081db7b..2f8b139 100644
--- a/src/runtime/select.go
+++ b/src/runtime/select.go
@@ -26,11 +26,10 @@
// 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 @@
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 @@
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 @@
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 @@
goto retc
retc:
- if cas.releasetime > 0 {
- blockevent(cas.releasetime-t0, 1)
+ if caseReleaseTime > 0 {
+ blockevent(caseReleaseTime-t0, 1)
}
return casi, recvOK
