Re: [PATCH 0/2] x86/idle: add halt poll support

[Yang Zhang]

On 2017/6/22 19:50, Wanpeng Li wrote:
> 2017-06-22 19:22 GMT+08:00 root <yang.zhang.wz@xxxxxxxxx>:
> > From: Yang Zhang <yang.zhang.wz@xxxxxxxxx>
> >
> > Some latency-intensive workload will see obviously performance
> > drop when running inside VM. The main reason is that the overhead
> > is amplified when running inside VM. The most cost i have seen is
> > inside idle path.
> > This patch introduces a new mechanism to poll for a while before
> > entering idle state. If schedule is needed during poll, then we
> > don't need to goes through the heavy overhead path.
> >
> > Here is the data i get when running benchmark contextswitch
> > (https://github.com/tsuna/contextswitch)
> > before patch:
> > 2000000 process context switches in 4822613801ns (2411.3ns/ctxsw)
> > after patch:
> > 2000000 process context switches in 3584098241ns (1792.0ns/ctxsw)
>
> If you test this after disabling the adaptive halt-polling in kvm?
> What's the performance data of w/ this patchset and w/o the adaptive
> halt-polling in kvm, and w/o this patchset and w/ the adaptive
> halt-polling in kvm? In addition, both linux and windows guests can
> get benefit as we have already done this in kvm.

I will provide more data in next version. But it doesn't conflict with 
current halt polling inside kvm. This is just another enhancement.

> Regards,
> Wanpeng Li
>
> > Yang Zhang (2):
> >   x86/idle: add halt poll for halt idle
> >   x86/idle: use dynamic halt poll
> >
> >  Documentation/sysctl/kernel.txt          | 24 ++++++++++
> >  arch/x86/include/asm/processor.h         |  6 +++
> >  arch/x86/kernel/apic/apic.c              |  6 +++
> >  arch/x86/kernel/apic/vector.c            |  1 +
> >  arch/x86/kernel/cpu/mcheck/mce_amd.c     |  2 +
> >  arch/x86/kernel/cpu/mcheck/therm_throt.c |  2 +
> >  arch/x86/kernel/cpu/mcheck/threshold.c   |  2 +
> >  arch/x86/kernel/irq.c                    |  5 ++
> >  arch/x86/kernel/irq_work.c               |  2 +
> >  arch/x86/kernel/process.c                | 80 ++++++++++++++++++++++++++++++++
> >  arch/x86/kernel/smp.c                    |  6 +++
> >  include/linux/kernel.h                   |  5 ++
> >  kernel/sched/idle.c                      |  3 ++
> >  kernel/sysctl.c                          | 23 +++++++++
> >  14 files changed, 167 insertions(+)
> >
> > --
> > 1.8.3.1


--
Yang
Alibaba Cloud Computing