From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Quan Xu <quan.xu03@gmail.com>
Cc: Yang Zhang <yang.zhang.wz@gmail.com>,
kvm@vger.kernel.org, linux-doc@vger.kernel.org, x86@kernel.org,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org,
linux-fsdevel@vger.kernel.org, xen-devel@lists.xenproject.org
Subject: Re: [Xen-devel] [PATCH RFC v3 0/6] x86/idle: add halt poll support
Date: Wed, 15 Nov 2017 16:31:31 -0500 [thread overview]
Message-ID: <20171115213131.GB21113@char.us.oracle.com> (raw)
In-Reply-To: <1510567565-5118-1-git-send-email-quan.xu0@gmail.com>
On Mon, Nov 13, 2017 at 06:05:59PM +0800, Quan Xu wrote:
> From: Yang Zhang <yang.zhang.wz@gmail.com>
>
> Some latency-intensive workload have seen 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.
Meaning an VMEXIT b/c it is an 'halt' operation ? And then going
back in guest (VMRESUME) takes time. And hence your latency gets
all whacked b/c of this?
So if I understand - you want to use your _full_ timeslice (of the guest)
without ever (or as much as possible) to go in the hypervisor?
Which means in effect you don't care about power-saving or CPUfreq
savings, you just want to eat the full CPU for snack?
>
> 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.
Schedule of what? The guest or the host?
next prev parent reply other threads:[~2017-11-15 21:31 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1510567565-5118-1-git-send-email-quan.xu0@gmail.com>
2017-11-13 10:06 ` [PATCH RFC v3 1/6] x86/paravirt: Add pv_idle_ops to paravirt ops Quan Xu
2017-11-13 10:06 ` [PATCH RFC v3 2/6] KVM guest: register kvm_idle_poll for pv_idle_ops Quan Xu
2017-11-13 10:06 ` [PATCH RFC v3 3/6] sched/idle: Add a generic poll before enter real idle path Quan Xu
[not found] ` <1510567565-5118-2-git-send-email-quan.xu0@gmail.com>
2017-11-13 10:53 ` [PATCH RFC v3 1/6] x86/paravirt: Add pv_idle_ops to paravirt ops Juergen Gross
[not found] ` <07fac696-e3d4-8f35-8f3d-764d7ab41204@suse.com>
2017-11-13 11:09 ` Wanpeng Li
2017-11-14 7:02 ` Quan Xu
[not found] ` <902da704-1e4f-583b-91c3-1a62ccd6e73d@gmail.com>
2017-11-14 7:12 ` Wanpeng Li
2017-11-14 7:30 ` Juergen Gross
[not found] ` <CANRm+CxirO0aSAQnOfPG0+KPCOnXf3SEASwBiprLmtncZE53pA@mail.gmail.com>
2017-11-14 8:15 ` Quan Xu
[not found] ` <d233b179-9815-0134-ef04-c492f9523121@gmail.com>
2017-11-14 8:22 ` Wanpeng Li
2017-11-14 10:23 ` Quan Xu
[not found] ` <fe6eeed1-4eee-eaaa-df3b-8979af8a3891@suse.com>
2017-11-14 9:38 ` Quan Xu
[not found] ` <79dad15c-2d26-bcf3-7283-293e42a161ea@gmail.com>
2017-11-14 10:27 ` Juergen Gross
[not found] ` <9a4f53f3-225f-0e99-d9b2-d89656b8fb31@suse.com>
2017-11-14 11:43 ` Quan Xu
[not found] ` <41403bbb-bfa9-0618-abf7-dd871a7b783a@gmail.com>
2017-11-14 11:58 ` Juergen Gross
[not found] ` <1510567565-5118-4-git-send-email-quan.xu0@gmail.com>
2017-11-15 12:11 ` [PATCH RFC v3 3/6] sched/idle: Add a generic poll before enter real idle path Peter Zijlstra
2017-11-15 22:03 ` Thomas Gleixner
[not found] ` <alpine.DEB.2.20.1711152240010.2146@nanos>
2017-11-16 8:45 ` Peter Zijlstra
2017-11-16 8:58 ` Thomas Gleixner
2017-11-16 9:29 ` Quan Xu
[not found] ` <13a3a5c5-ec14-131f-fe6a-01700783de81@gmail.com>
2017-11-16 9:47 ` Thomas Gleixner
2017-11-16 9:12 ` Quan Xu
[not found] ` <46086489-5a01-16e1-9314-70ae53c01952@gmail.com>
2017-11-16 9:45 ` Daniel Lezcano
2017-11-16 9:53 ` Thomas Gleixner
[not found] ` <alpine.DEB.2.20.1711161048000.2191@nanos>
2017-11-17 11:23 ` Quan Xu
[not found] ` <564b8a6e-8ddd-4e3d-c670-10f1697e6c06@gmail.com>
2017-11-17 11:36 ` Thomas Gleixner
2017-11-17 12:21 ` Quan Xu
[not found] ` <93a26005-aa37-82e1-5c04-a82c9027bac8@linaro.org>
2017-11-20 7:05 ` Quan Xu
[not found] ` <5deab1e9-cef2-0511-09d8-cef8e4323f02@gmail.com>
2017-11-20 18:01 ` Daniel Lezcano
2017-11-15 21:31 ` Konrad Rzeszutek Wilk [this message]
2017-11-20 7:18 ` [Xen-devel] [PATCH RFC v3 0/6] x86/idle: add halt poll support Quan Xu
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=20171115213131.GB21113@char.us.oracle.com \
--to=konrad.wilk@oracle.com \
--cc=kvm@vger.kernel.org \
--cc=linux-doc@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=quan.xu03@gmail.com \
--cc=virtualization@lists.linux-foundation.org \
--cc=x86@kernel.org \
--cc=xen-devel@lists.xenproject.org \
--cc=yang.zhang.wz@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).