From 58a1dabfd1b2bbc2a6a9a2e1cda3e98d93d61258 Mon Sep 17 00:00:00 2001 From: Michael Pratt Date: Wed, 20 Jul 2022 18:01:31 -0400 Subject: [PATCH] runtime: convert schedt.npidle to atomic type Note that this converts npidle from uint32 to int32 for consistency with the other count fields in schedt and the type of p.id. Note that this changes previously unsynchronized operations to synchronized operations in: * handoffp * injectglist * schedtrace * schedEnableUser * sync_runtime_canSpin For #53821. Change-Id: I36d1b3b4a28131c9d47884fade6bc44439dd6937 Reviewed-on: https://go-review.googlesource.com/c/go/+/419445 TryBot-Result: Gopher Robot Reviewed-by: Austin Clements Run-TryBot: Michael Pratt --- src/runtime/mgcpacer.go | 2 +- src/runtime/proc.go | 29 ++++++++++++++--------------- src/runtime/runtime2.go | 2 +- 3 files changed, 16 insertions(+), 17 deletions(-) diff --git a/src/runtime/mgcpacer.go b/src/runtime/mgcpacer.go index 24f856740e..9e12e4c8db 100644 --- a/src/runtime/mgcpacer.go +++ b/src/runtime/mgcpacer.go @@ -750,7 +750,7 @@ func (c *gcControllerState) enlistWorker() { // If there are idle Ps, wake one so it will run an idle worker. // NOTE: This is suspected of causing deadlocks. See golang.org/issue/19112. // - // if atomic.Load(&sched.npidle) != 0 && atomic.Load(&sched.nmspinning) == 0 { + // if sched.npidle.Load() != 0 && atomic.Load(&sched.nmspinning) == 0 { // wakep() // return // } diff --git a/src/runtime/proc.go b/src/runtime/proc.go index 55c82ffa3e..9cad2161b5 100644 --- a/src/runtime/proc.go +++ b/src/runtime/proc.go @@ -2362,7 +2362,7 @@ func handoffp(pp *p) { } // no local work, check that there are no spinning/idle M's, // otherwise our help is not required - if atomic.Load(&sched.nmspinning)+atomic.Load(&sched.npidle) == 0 && atomic.Cas(&sched.nmspinning, 0, 1) { // TODO: fast atomic + if int32(atomic.Load(&sched.nmspinning))+sched.npidle.Load() == 0 && atomic.Cas(&sched.nmspinning, 0, 1) { // TODO: fast atomic startm(pp, true) return } @@ -2390,7 +2390,7 @@ func handoffp(pp *p) { } // If this is the last running P and nobody is polling network, // need to wakeup another M to poll network. - if sched.npidle == uint32(gomaxprocs-1) && sched.lastpoll.Load() != 0 { + if sched.npidle.Load() == gomaxprocs-1 && sched.lastpoll.Load() != 0 { unlock(&sched.lock) startm(pp, false) return @@ -2410,7 +2410,7 @@ func handoffp(pp *p) { // Tries to add one more P to execute G's. // Called when a G is made runnable (newproc, ready). func wakep() { - if atomic.Load(&sched.npidle) == 0 { + if sched.npidle.Load() == 0 { return } // be conservative about spinning threads @@ -2649,8 +2649,7 @@ top: // Limit the number of spinning Ms to half the number of busy Ps. // This is necessary to prevent excessive CPU consumption when // GOMAXPROCS>>1 but the program parallelism is low. - procs := uint32(gomaxprocs) - if mp.spinning || 2*atomic.Load(&sched.nmspinning) < procs-atomic.Load(&sched.npidle) { + if mp.spinning || int32(2*atomic.Load(&sched.nmspinning)) < gomaxprocs-sched.npidle.Load() { if !mp.spinning { mp.spinning = true atomic.Xadd(&sched.nmspinning, 1) @@ -3136,7 +3135,7 @@ func injectglist(glist *gList) { *glist = gList{} startIdle := func(n int) { - for ; n != 0 && sched.npidle != 0; n-- { + for ; n != 0 && sched.npidle.Load() != 0; n-- { startm(nil, false) } } @@ -3150,7 +3149,7 @@ func injectglist(glist *gList) { return } - npidle := int(atomic.Load(&sched.npidle)) + npidle := int(sched.npidle.Load()) var globq gQueue var n int for n = 0; n < npidle && !q.empty(); n++ { @@ -5156,9 +5155,9 @@ func sysmon() { // from a timer to avoid adding system load to applications that spend // most of their time sleeping. now := nanotime() - if debug.schedtrace <= 0 && (sched.gcwaiting != 0 || atomic.Load(&sched.npidle) == uint32(gomaxprocs)) { + if debug.schedtrace <= 0 && (sched.gcwaiting != 0 || sched.npidle.Load() == gomaxprocs) { lock(&sched.lock) - if atomic.Load(&sched.gcwaiting) != 0 || atomic.Load(&sched.npidle) == uint32(gomaxprocs) { + if atomic.Load(&sched.gcwaiting) != 0 || sched.npidle.Load() == gomaxprocs { syscallWake := false next := timeSleepUntil() if next > now { @@ -5318,7 +5317,7 @@ func retake(now int64) uint32 { // 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 runqempty(pp) && atomic.Load(&sched.nmspinning)+atomic.Load(&sched.npidle) > 0 && pd.syscallwhen+10*1000*1000 > now { + if runqempty(pp) && atomic.Load(&sched.nmspinning)+uint32(sched.npidle.Load()) > 0 && pd.syscallwhen+10*1000*1000 > now { continue } // Drop allpLock so we can take sched.lock. @@ -5409,7 +5408,7 @@ func schedtrace(detailed bool) { } lock(&sched.lock) - print("SCHED ", (now-starttime)/1e6, "ms: gomaxprocs=", gomaxprocs, " idleprocs=", sched.npidle, " threads=", mcount(), " spinningthreads=", sched.nmspinning, " idlethreads=", sched.nmidle, " runqueue=", sched.runqsize) + print("SCHED ", (now-starttime)/1e6, "ms: gomaxprocs=", gomaxprocs, " idleprocs=", sched.npidle.Load(), " threads=", mcount(), " spinningthreads=", sched.nmspinning, " idlethreads=", sched.nmidle, " runqueue=", sched.runqsize) if detailed { print(" gcwaiting=", sched.gcwaiting, " nmidlelocked=", sched.nmidlelocked, " stopwait=", sched.stopwait, " sysmonwait=", sched.sysmonwait, "\n") } @@ -5505,7 +5504,7 @@ func schedEnableUser(enable bool) { sched.disable.n = 0 globrunqputbatch(&sched.disable.runnable, n) unlock(&sched.lock) - for ; n != 0 && sched.npidle != 0; n-- { + for ; n != 0 && sched.npidle.Load() != 0; n-- { startm(nil, false) } } else { @@ -5713,7 +5712,7 @@ func pidleput(pp *p, now int64) int64 { idlepMask.set(pp.id) pp.link = sched.pidle sched.pidle.set(pp) - atomic.Xadd(&sched.npidle, 1) + sched.npidle.Add(1) if !pp.limiterEvent.start(limiterEventIdle, now) { throw("must be able to track idle limiter event") } @@ -5739,7 +5738,7 @@ func pidleget(now int64) (*p, int64) { timerpMask.set(pp.id) idlepMask.clear(pp.id) sched.pidle = pp.link - atomic.Xadd(&sched.npidle, -1) + sched.npidle.Add(-1) pp.limiterEvent.stop(limiterEventIdle, now) } return pp, now @@ -6194,7 +6193,7 @@ func sync_runtime_canSpin(i int) bool { // GOMAXPROCS>1 and there is at least one other running P and local runq is empty. // As opposed to runtime mutex we don't do passive spinning here, // because there can be work on global runq or on other Ps. - if i >= active_spin || ncpu <= 1 || gomaxprocs <= int32(sched.npidle+sched.nmspinning)+1 { + if i >= active_spin || ncpu <= 1 || gomaxprocs <= sched.npidle.Load()+int32(sched.nmspinning)+1 { return false } if p := getg().m.p.ptr(); !runqempty(p) { diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go index bc482b00a2..7b43358ba1 100644 --- a/src/runtime/runtime2.go +++ b/src/runtime/runtime2.go @@ -778,7 +778,7 @@ type schedt struct { ngsys atomic.Int32 // number of system goroutines pidle puintptr // idle p's - npidle uint32 + npidle atomic.Int32 nmspinning uint32 // See "Worker thread parking/unparking" comment in proc.go. // Global runnable queue. -- 2.48.1