runtime: factor checking if P run queue is empty
There are a variety of places where we check if a P's run queue is
empty. This test is about to get slightly more complicated, so factor
it out into a new function, runqempty. This function is inlinable, so
this has no effect on performance.
Change-Id: If4a0b01ffbd004937de90d8d686f6ded4aad2c6b
Reviewed-on: https://go-review.googlesource.com/9287
Reviewed-by: Rick Hudson <rlh@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/src/runtime/proc1.go b/src/runtime/proc1.go
index 0359b55..d37c4f1 100644
--- a/src/runtime/proc1.go
+++ b/src/runtime/proc1.go
@@ -1115,7 +1115,7 @@
//go:nowritebarrier
func handoffp(_p_ *p) {
// if it has local work, start it straight away
- if _p_.runqhead != _p_.runqtail || sched.runqsize != 0 {
+ if !runqempty(_p_) || sched.runqsize != 0 {
startm(_p_, false)
return
}
@@ -1369,7 +1369,7 @@
// check all runqueues once again
for i := 0; i < int(gomaxprocs); i++ {
_p_ := allp[i]
- if _p_ != nil && _p_.runqhead != _p_.runqtail {
+ if _p_ != nil && !runqempty(_p_) {
lock(&sched.lock)
_p_ = pidleget()
unlock(&sched.lock)
@@ -2657,7 +2657,7 @@
continue
}
p.status = _Pidle
- if p.runqhead == p.runqtail {
+ if runqempty(p) {
pidleput(p)
} else {
p.m.set(mget())
@@ -2940,7 +2940,7 @@
// On the one hand we don't want to retake Ps if there is no other work to do,
// but on the other hand we want to retake them eventually
// because they can prevent the sysmon thread from deep sleep.
- if _p_.runqhead == _p_.runqtail && atomicload(&sched.nmspinning)+atomicload(&sched.npidle) > 0 && pd.syscallwhen+10*1000*1000 > now {
+ if runqempty(_p_) && atomicload(&sched.nmspinning)+atomicload(&sched.npidle) > 0 && pd.syscallwhen+10*1000*1000 > now {
continue
}
// Need to decrement number of idle locked M's
@@ -3220,6 +3220,12 @@
return _p_
}
+// runqempty returns true if _p_ has no Gs on its local run queue.
+// Note that this test is generally racy.
+func runqempty(_p_ *p) bool {
+ return _p_.runqhead == _p_.runqtail
+}
+
// Try to put g on local runnable queue.
// If it's full, put onto global queue.
// Executed only by the owner P.
@@ -3479,7 +3485,7 @@
if i >= active_spin || ncpu <= 1 || gomaxprocs <= int32(sched.npidle+sched.nmspinning)+1 {
return false
}
- if p := getg().m.p.ptr(); p.runqhead != p.runqtail {
+ if p := getg().m.p.ptr(); !runqempty(p) {
return false
}
return true
