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

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Date:   Thu, 22 Jun 2017 19:50:02 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     root <yang.zhang.wz@...il.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Jonathan Corbet <corbet@....net>, tony.luck@...el.com,
        Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>, mchehab@...nel.org,
        Andrew Morton <akpm@...ux-foundation.org>, krzk@...nel.org,
        jpoimboe@...hat.com, Andy Lutomirski <luto@...nel.org>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        thgarnie@...gle.com, rgerst@...il.com, minipli@...glemail.com,
        douly.fnst@...fujitsu.com, nicstange@...il.com,
        Frederic Weisbecker <fweisbec@...il.com>, dvlasenk@...hat.com,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        yamada.masahiro@...ionext.com, mika.westerberg@...ux.intel.com,
        Chen Yu <yu.c.chen@...el.com>, aaron.lu@...el.com,
        Steven Rostedt <rostedt@...dmis.org>, me@...ehuey.com,
        Len Brown <len.brown@...el.com>,
        Prarit Bhargava <prarit@...hat.com>,
        hidehiro.kawai.ez@...achi.com, fengtiantian@...wei.com,
        pmladek@...e.com, jeyu@...hat.com, Larry.Finger@...inger.net,
        zijun_hu@....com, luisbg@....samsung.com, johannes.berg@...el.com,
        niklas.soderlund+renesas@...natech.se, zlpnobody@...il.com,
        adobriyan@...il.com, fgao@...ai8.com, ebiederm@...ssion.com,
        subashab@...eaurora.org, arnd@...db.de,
        Matt Fleming <matt@...eblueprint.co.uk>,
        Mel Gorman <mgorman@...hsingularity.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        linux-doc@...r.kernel.org, linux-edac@...r.kernel.org,
        kvm <kvm@...r.kernel.org>
Subject: Re: [PATCH 0/2] x86/idle: add halt poll support

2017-06-22 19:22 GMT+08:00 root <yang.zhang.wz@...il.com>:
> From: Yang Zhang <yang.zhang.wz@...il.com>
>
> 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
>