Re: sched_rt_period_timer causing large latencies

2018-04-06 Thread Peter Zijlstra
On Thu, Apr 05, 2018 at 08:08:59PM +1000, Nicholas Piggin wrote: > On Thu, 05 Apr 2018 10:40:20 +0200 > Mike Galbraith wrote: > > > On Thu, 2018-04-05 at 10:27 +0200, Peter Zijlstra wrote: > > > On Thu, Apr 05, 2018 at 09:11:38AM +1000, Nicholas Piggin wrote: > > > > Hi, > > > > > > > > I'm se

Re: sched_rt_period_timer causing large latencies

2018-04-05 Thread Nicholas Piggin
On Thu, 5 Apr 2018 20:08:59 +1000 Nicholas Piggin wrote: > On Thu, 05 Apr 2018 10:40:20 +0200 > Mike Galbraith wrote: > > > On Thu, 2018-04-05 at 10:27 +0200, Peter Zijlstra wrote: > > > On Thu, Apr 05, 2018 at 09:11:38AM +1000, Nicholas Piggin wrote: > > > > Hi, > > > > > > > > I'm seei

Re: sched_rt_period_timer causing large latencies

2018-04-05 Thread Nicholas Piggin
On Thu, 05 Apr 2018 10:40:20 +0200 Mike Galbraith wrote: > On Thu, 2018-04-05 at 10:27 +0200, Peter Zijlstra wrote: > > On Thu, Apr 05, 2018 at 09:11:38AM +1000, Nicholas Piggin wrote: > > > Hi, > > > > > > I'm seeing some pretty big latencies on a ~idle system when a CPU wakes > > > out of a

Re: sched_rt_period_timer causing large latencies

2018-04-05 Thread Mike Galbraith
On Thu, 2018-04-05 at 10:27 +0200, Peter Zijlstra wrote: > On Thu, Apr 05, 2018 at 09:11:38AM +1000, Nicholas Piggin wrote: > > Hi, > > > > I'm seeing some pretty big latencies on a ~idle system when a CPU wakes > > out of a nohz idle. Looks like it's due to the taking a lot of remote > > locks an

Re: sched_rt_period_timer causing large latencies

2018-04-05 Thread Peter Zijlstra
On Thu, Apr 05, 2018 at 09:11:38AM +1000, Nicholas Piggin wrote: > Hi, > > I'm seeing some pretty big latencies on a ~idle system when a CPU wakes > out of a nohz idle. Looks like it's due to the taking a lot of remote > locks and cache lines. irqoff trace: On RT I think we default RT_RUNTIME_SHA

Re: sched_rt_period_timer causing large latencies

2018-04-05 Thread Mike Galbraith
On Thu, 2018-04-05 at 17:44 +1000, Nicholas Piggin wrote: > > > My method of dealing with the throttle beast from hell for ~big box RT > > is to stomp it flat during boot, as otherwise jitter is awful. > > How do you stomp it flat? With a size 12 boot originally from SGI. Their extra hairy beas

Re: sched_rt_period_timer causing large latencies

2018-04-05 Thread Nicholas Piggin
On Thu, 05 Apr 2018 08:46:57 +0200 Mike Galbraith wrote: > On Thu, 2018-04-05 at 09:11 +1000, Nicholas Piggin wrote: > > Hi, > > > > I'm seeing some pretty big latencies on a ~idle system when a CPU wakes > > out of a nohz idle. Looks like it's due to the taking a lot of remote > > locks and cac

Re: sched_rt_period_timer causing large latencies

2018-04-04 Thread Mike Galbraith
On Thu, 2018-04-05 at 09:11 +1000, Nicholas Piggin wrote: > Hi, > > I'm seeing some pretty big latencies on a ~idle system when a CPU wakes > out of a nohz idle. Looks like it's due to the taking a lot of remote > locks and cache lines. irqoff trace: > > latency: 407 us, #608/608, CPU#3 | (M:serv

sched_rt_period_timer causing large latencies

2018-04-04 Thread Nicholas Piggin
Hi, I'm seeing some pretty big latencies on a ~idle system when a CPU wakes out of a nohz idle. Looks like it's due to the taking a lot of remote locks and cache lines. irqoff trace: latency: 407 us, #608/608, CPU#3 | (M:server VP:0, KP:0, SP:0 HP:0 #P:176) -0 3d...0us : decrementer_