From: Wanpeng Li <kernellwp@gmail.com>
To: Yang Zhang <yang.zhang.wz@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
Paolo Bonzini <pbonzini@redhat.com>,
"the arch/x86 maintainers" <x86@kernel.org>,
Jonathan Corbet <corbet@lwn.net>,
tony.luck@intel.com, Borislav Petkov <bp@alien8.de>,
Peter Zijlstra <peterz@infradead.org>,
mchehab@kernel.org, Andrew Morton <akpm@linux-foundation.org>,
krzk@kernel.org, jpoimboe@redhat.com,
Andy Lutomirski <luto@kernel.org>,
Christian Borntraeger <borntraeger@de.ibm.com>,
Thomas Garnier <thgarnie@google.com>,
Robert Gerst <rgerst@gmail.com>,
Mathias Krause <minipli@googlemail.com>,
douly.fnst@cn.fujitsu.com, Nicolai Stange <nicstange@gmail.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
dvlasenk@redhat.com,
Daniel Bristot de Oliveira <bristot@redhat.com>,
yamada.masahiro@socionext.com, mika.westerberg@linux.intel.com,
Chen Yu <yu.c.chen@intel.com>,
aaron.lu@intel.com, Steven Rostedt <rostedt@goodmis.org>,
Kyle Huey <me@kylehuey.com>, Len Brown <len.brown@intel.com>,
Prarit Bhargava <prarit@redhat.com>,
hidehiro.kawai.ez@hitachi.com, fengtiantian@huawei.com,
pmladek@suse.com, jeyu@redhat.com, Larry.Finger@lwfinger.net,
zijun_hu@htc.com, luisbg@osg.samsung.com,
johannes.berg@intel.com, niklas.soderlund+renesas@ragnatech.se,
zlpnobody@gmail.com, Alexey Dobriyan <adobriyan@gmail.com>,
fgao@48lvckh6395k16k5.yundunddos.com, ebiederm@xmission.com,
Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>,
Arnd Bergmann <arnd@arndb.de>,
Matt Fleming <matt@codeblueprint.co.uk>,
Mel Gorman <mgorman@techsingularity.net>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
linux-doc@vger.kernel.org, linux-edac@vger.kernel.org,
kvm <kvm@vger.kernel.org>
Subject: Re: [PATCH 0/2] x86/idle: add halt poll support
Date: Fri, 23 Jun 2017 12:35:59 +0800 [thread overview]
Message-ID: <CANRm+CzYm-_tzK+zLU8n5BCRx8u=80ECo9-Jhmwa9UHLTQVAzA@mail.gmail.com> (raw)
In-Reply-To: <a3e1866d-7fb2-9f81-93e7-6b9ff6609e13@gmail.com>
2017-06-23 12:08 GMT+08:00 Yang Zhang <yang.zhang.wz@gmail.com>:
> On 2017/6/22 19:50, Wanpeng Li wrote:
>>
>> 2017-06-22 19:22 GMT+08:00 root <yang.zhang.wz@gmail.com>:
>>>
>>> From: Yang Zhang <yang.zhang.wz@gmail.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
Another case I can think of is w/ both this patchset and the adaptive
halt-polling in kvm.
> current halt polling inside kvm. This is just another enhancement.
I didn't look close to the patchset, however, maybe there is another
poll in the kvm part again sometimes if you fails the poll in the
guest. In addition, the adaptive halt-polling in kvm has performance
penalty when the pCPU is heavily overcommitted though there is a
single_task_running() in my testing, it is hard to accurately aware
whether there are other tasks waiting on the pCPU in the guest which
will make it worser. Depending on vcpu_is_preempted() or steal time
maybe not accurately or directly.
So I'm not sure how much sense it makes by adaptive halt-polling in
both guest and kvm. I prefer to just keep adaptive halt-polling in
kvm(then both linux/windows or other guests can get benefit) and avoid
to churn the core x86 path.
Regards,
Wanpeng Li
next prev parent reply other threads:[~2017-06-23 4:36 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-22 11:22 [PATCH 0/2] x86/idle: add halt poll support root
2017-06-22 11:22 ` [PATCH 1/2] x86/idle: add halt poll for halt idle root
2017-06-22 14:23 ` Thomas Gleixner
2017-06-23 4:05 ` Yang Zhang
2017-08-16 4:04 ` Michael S. Tsirkin
2017-08-17 7:29 ` Yang Zhang
2017-06-22 11:22 ` [PATCH 2/2] x86/idle: use dynamic halt poll root
2017-06-22 11:51 ` Paolo Bonzini
2017-06-23 3:58 ` Yang Zhang
2017-06-27 11:22 ` Yang Zhang
2017-06-27 12:07 ` Paolo Bonzini
2017-06-27 12:23 ` Wanpeng Li
2017-06-27 12:28 ` Paolo Bonzini
2017-06-27 13:40 ` Radim Krčmář
2017-06-27 13:56 ` Paolo Bonzini
2017-06-27 14:22 ` Radim Krčmář
2017-06-27 14:26 ` Paolo Bonzini
2017-07-03 9:28 ` Yang Zhang
2017-07-03 10:06 ` Thomas Gleixner
2017-07-04 2:19 ` Yang Zhang
2017-07-04 14:13 ` Radim Krčmář
2017-07-04 14:50 ` Thomas Gleixner
2017-07-13 11:49 ` Yang Zhang
2017-07-14 9:37 ` Alexander Graf
2017-07-17 9:26 ` Yang Zhang
2017-07-17 9:54 ` Alexander Graf
2017-07-17 12:50 ` Yang Zhang
2017-07-04 22:28 ` Wanpeng Li
2017-06-22 14:32 ` Thomas Gleixner
2017-06-23 4:04 ` Yang Zhang
2017-06-22 22:46 ` kbuild test robot
2017-06-22 11:32 ` [PATCH 0/2] x86/idle: add halt poll support Yang Zhang
2017-06-22 11:50 ` Wanpeng Li
2017-06-23 4:08 ` Yang Zhang
2017-06-23 4:35 ` Wanpeng Li [this message]
2017-06-23 6:49 ` Yang Zhang
2017-06-27 14:00 ` Radim Krčmář
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='CANRm+CzYm-_tzK+zLU8n5BCRx8u=80ECo9-Jhmwa9UHLTQVAzA@mail.gmail.com' \
--to=kernellwp@gmail.com \
--cc=Larry.Finger@lwfinger.net \
--cc=aaron.lu@intel.com \
--cc=adobriyan@gmail.com \
--cc=akpm@linux-foundation.org \
--cc=arnd@arndb.de \
--cc=borntraeger@de.ibm.com \
--cc=bp@alien8.de \
--cc=bristot@redhat.com \
--cc=corbet@lwn.net \
--cc=douly.fnst@cn.fujitsu.com \
--cc=dvlasenk@redhat.com \
--cc=ebiederm@xmission.com \
--cc=fengtiantian@huawei.com \
--cc=fgao@48lvckh6395k16k5.yundunddos.com \
--cc=fweisbec@gmail.com \
--cc=hidehiro.kawai.ez@hitachi.com \
--cc=hpa@zytor.com \
--cc=jeyu@redhat.com \
--cc=johannes.berg@intel.com \
--cc=jpoimboe@redhat.com \
--cc=krzk@kernel.org \
--cc=kvm@vger.kernel.org \
--cc=len.brown@intel.com \
--cc=linux-doc@vger.kernel.org \
--cc=linux-edac@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luisbg@osg.samsung.com \
--cc=luto@kernel.org \
--cc=matt@codeblueprint.co.uk \
--cc=mchehab@kernel.org \
--cc=me@kylehuey.com \
--cc=mgorman@techsingularity.net \
--cc=mika.westerberg@linux.intel.com \
--cc=mingo@redhat.com \
--cc=minipli@googlemail.com \
--cc=nicstange@gmail.com \
--cc=niklas.soderlund+renesas@ragnatech.se \
--cc=pbonzini@redhat.com \
--cc=peterz@infradead.org \
--cc=pmladek@suse.com \
--cc=prarit@redhat.com \
--cc=rgerst@gmail.com \
--cc=rostedt@goodmis.org \
--cc=subashab@codeaurora.org \
--cc=tglx@linutronix.de \
--cc=thgarnie@google.com \
--cc=tony.luck@intel.com \
--cc=x86@kernel.org \
--cc=yamada.masahiro@socionext.com \
--cc=yang.zhang.wz@gmail.com \
--cc=yu.c.chen@intel.com \
--cc=zijun_hu@htc.com \
--cc=zlpnobody@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).