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

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Date:   Fri, 23 Jun 2017 12:08:16 +0800
From:   Yang Zhang <yang.zhang.wz@...il.com>
To:     Wanpeng Li <kernellwp@...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

On 2017/6/22 19:50, Wanpeng Li wrote:
> 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.

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