Re: [PATCH v2] sched/nohz: Optimize get_nohz_timer_target()

2019-10-23 Thread Wanpeng Li
On Wed, 23 Oct 2019 at 16:29, Thomas Gleixner wrote: > > On Wed, 23 Oct 2019, Wanpeng Li wrote: > > I didn't see your refactor to get_nohz_timer_target() which you > > mentioned in IRC after four months, I can observe cyclictest drop from > > 4~5us to 8us in kvm guest(we offload the lapic timer em

Re: [PATCH v2] sched/nohz: Optimize get_nohz_timer_target()

2019-10-23 Thread Thomas Gleixner
On Wed, 23 Oct 2019, Wanpeng Li wrote: > I didn't see your refactor to get_nohz_timer_target() which you > mentioned in IRC after four months, I can observe cyclictest drop from > 4~5us to 8us in kvm guest(we offload the lapic timer emulation to > housekeeping cpu to avoid timer fire external inter

Re: [PATCH v2] sched/nohz: Optimize get_nohz_timer_target()

2019-10-23 Thread Wanpeng Li
On Fri, 28 Jun 2019 at 09:10, Frederic Weisbecker wrote: > > On Fri, Jun 28, 2019 at 08:43:12AM +0800, Wanpeng Li wrote: > > From: Wanpeng Li > > > > On a machine, cpu 0 is used for housekeeping, the other 39 cpus in the > > same socket are in nohz_full mode. We can observe huge time burn in the

Re: [PATCH v2] sched/nohz: Optimize get_nohz_timer_target()

2019-06-27 Thread Frederic Weisbecker
On Fri, Jun 28, 2019 at 08:43:12AM +0800, Wanpeng Li wrote: > From: Wanpeng Li > > On a machine, cpu 0 is used for housekeeping, the other 39 cpus in the > same socket are in nohz_full mode. We can observe huge time burn in the > loop for seaching nearest busy housekeeper cpu by ftrace. > >

[PATCH v2] sched/nohz: Optimize get_nohz_timer_target()

2019-06-27 Thread Wanpeng Li
From: Wanpeng Li On a machine, cpu 0 is used for housekeeping, the other 39 cpus in the same socket are in nohz_full mode. We can observe huge time burn in the loop for seaching nearest busy housekeeper cpu by ftrace. 2) | get_nohz_timer_target() { 2) 0.240 us|