From: Peter Zijlstra <peterz@infradead.org>
To: "Raslan, KarimAllah" <karahmed@amazon.de>
Cc: "boris.ostrovsky@oracle.com" <boris.ostrovsky@oracle.com>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"kernellwp@gmail.com" <kernellwp@gmail.com>,
"joao.m.martins@oracle.com" <joao.m.martins@oracle.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"konrad.wilk@oracle.com" <konrad.wilk@oracle.com>,
"mtosatti@redhat.com" <mtosatti@redhat.com>,
"pbonzini@redhat.com" <pbonzini@redhat.com>,
"ankur.a.arora@oracle.com" <ankur.a.arora@oracle.com>,
"rkrcmar@redhat.com" <rkrcmar@redhat.com>
Subject: Re: cputime takes cstate into consideration
Date: Wed, 26 Jun 2019 22:01:26 +0200 [thread overview]
Message-ID: <20190626200126.GQ3419@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <1561577254.25880.15.camel@amazon.de>
On Wed, Jun 26, 2019 at 07:27:35PM +0000, Raslan, KarimAllah wrote:
> On Wed, 2019-06-26 at 21:21 +0200, Peter Zijlstra wrote:
> > On Wed, Jun 26, 2019 at 06:55:36PM +0000, Raslan, KarimAllah wrote:
> >
> > >
> > > If the host is completely in no_full_hz mode and the pCPU is dedicated to a
> > > single vCPU/task (and the guest is 100% CPU bound and never exits), you would
> > > still be ticking in the host once every second for housekeeping, right? Would
> > > not updating the mwait-time once a second be enough here?
> >
> > People are trying very hard to get rid of that remnant tick. Lets not
> > add dependencies to it.
> >
> > IMO this is a really stupid issue, 100% time is correct if the guest
> > does idle in pinned vcpu mode.
>
> One use case for proper accounting (obviously for a slightly relaxed definition
> or *proper*) is *external* monitoring of CPU utilization for scaling group
> (i.e. more VMs will be launched when you reach a certain CPU utilization).
> These external monitoring tools needs to account CPU utilization properly.
That's utter nonsense; what's the point of exposing mwait to guests if
you're not doing vcpu pinning. For overloaded guests mwait makes no
sense what so ever.
next prev parent reply other threads:[~2019-06-26 20:01 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-26 9:43 cputime takes cstate into consideration Wanpeng Li
2019-06-26 10:13 ` Peter Zijlstra
2019-06-26 10:33 ` Thomas Gleixner
2019-06-26 14:54 ` Konrad Rzeszutek Wilk
2019-06-26 16:16 ` Peter Zijlstra
2019-06-26 18:30 ` Konrad Rzeszutek Wilk
2019-06-26 18:41 ` Thomas Gleixner
2019-06-26 18:55 ` Raslan, KarimAllah
2019-06-26 19:19 ` Thomas Gleixner
2019-06-26 19:21 ` Peter Zijlstra
2019-06-26 19:27 ` Raslan, KarimAllah
2019-06-26 19:32 ` Thomas Gleixner
2019-06-26 20:01 ` Peter Zijlstra [this message]
2019-06-26 20:09 ` Thomas Gleixner
2019-12-10 0:44 ` Wanpeng Li
2019-06-26 19:29 ` Thomas Gleixner
2019-06-26 18:58 ` Raslan, KarimAllah
2019-06-26 19:23 ` Thomas Gleixner
2019-07-09 2:00 ` Ankur Arora
2019-07-09 2:06 ` Wanpeng Li
2019-07-09 12:38 ` Peter Zijlstra
2019-07-09 18:27 ` Ankur Arora
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=20190626200126.GQ3419@hirez.programming.kicks-ass.net \
--to=peterz@infradead.org \
--cc=ankur.a.arora@oracle.com \
--cc=boris.ostrovsky@oracle.com \
--cc=joao.m.martins@oracle.com \
--cc=karahmed@amazon.de \
--cc=kernellwp@gmail.com \
--cc=konrad.wilk@oracle.com \
--cc=kvm@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mtosatti@redhat.com \
--cc=pbonzini@redhat.com \
--cc=rkrcmar@redhat.com \
--cc=tglx@linutronix.de \
/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).