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

[Wanpeng Li]

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.

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
>