From: Jan Beulich <JBeulich@suse.com>
To: Dario Faggioli <dfaggioli@suse.com>, Juergen Gross <JGross@suse.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>,
Konrad Wilk <konrad.wilk@oracle.com>,
George Dunlap <George.Dunlap@eu.citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Tim Deegan <tim@xen.org>, Julien Grall <julien.grall@arm.com>,
Meng Xu <mengxu@cis.upenn.edu>,
"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
Ian Jackson <ian.jackson@citrix.com>,
Roger Pau Monne <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH 13/60] xen/sched: move some per-vcpu items to struct sched_unit
Date: Tue, 2 Jul 2019 08:29:30 +0000 [thread overview]
Message-ID: <ae74f899-b3ea-6349-5352-88b07c0dc9d8@suse.com> (raw)
In-Reply-To: <ace01bb733d0dd624b9e9ee07c5da4f5567a8a8a.camel@suse.com>
On 02.07.2019 10:21, Dario Faggioli wrote:
> On Tue, 2019-07-02 at 07:54 +0000, Jan Beulich wrote:
>> On 02.07.2019 08:30, Juergen Gross wrote:
>>> On 01.07.19 17:46, Jan Beulich wrote:
>>>>
>>>> Hmm, that's indeed what I was deducing, but how will we sell this
>>>> to people actually fiddling with vCPU affinities? I foresee
>>>> getting
>>>> bug reports that the respective xl command(s) do(es)n't do
>>>> anymore
>>>> what it used to do.
>>>
>>> The new behavior must be documented, sure.
>>
>> Documentation is just one aspect. Often enough people only read docs
>> when wanting to introduce new functionality, which I consider a fair
>> model. Such people will be caught by surprise that the pinning
>> behavior does not work the same way anymore.
>>
> That is indeed the case, and we need to think about how to address it,
> I agree.
>
>> And again - if someone pins every vCPU to a single pCPU, that last
>> such pinning operation will be what takes long term effect. Aiui all
>> vCPU-s in the unit will then be pinned to that one pCPU, i.e.
>> they'll either all compete for the one pCPU's time, or only one of
>> them will ever get scheduled.
>>
> I'm not sure I'm getting this. On an, say, SMT system, with 4 threads
> per core, a unit is 4 vCPUs and a pCPU is 4 threads.
No, the meaning of pCPU is a single thread of a single core. I.e.
what is represented by a single cpumask_t bit.
Jan
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
next prev parent reply other threads:[~2019-07-02 8:30 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-01 14:08 [Xen-devel] [PATCH 13/60] xen/sched: move some per-vcpu items to struct sched_unit Jan Beulich
2019-07-01 15:10 ` Juergen Gross
2019-07-01 15:46 ` Jan Beulich
2019-07-02 6:30 ` Juergen Gross
2019-07-02 7:54 ` Jan Beulich
2019-07-02 8:14 ` Juergen Gross
2019-07-02 8:27 ` Jan Beulich
2019-07-02 8:44 ` Juergen Gross
2019-07-02 9:05 ` Jan Beulich
2019-07-02 9:16 ` Juergen Gross
2019-07-02 8:21 ` Dario Faggioli
2019-07-02 8:29 ` Jan Beulich [this message]
2019-07-02 9:40 ` Dario Faggioli
2019-07-02 10:01 ` Jan Beulich
2019-07-02 10:25 ` Juergen Gross
-- strict thread matches above, loose matches on Subject: below --
2019-05-28 10:32 [PATCH 00/60] xen: add core scheduling support Juergen Gross
2019-05-28 10:32 ` [Xen-devel] [PATCH 13/60] xen/sched: move some per-vcpu items to struct sched_unit Juergen Gross
2019-05-28 10:32 ` Juergen Gross
2019-06-13 7:18 ` Andrii Anisov
2019-06-13 7:29 ` Juergen Gross
2019-06-13 7:34 ` Andrii Anisov
2019-06-13 8:39 ` Juergen Gross
2019-06-13 8:49 ` Andrii Anisov
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=ae74f899-b3ea-6349-5352-88b07c0dc9d8@suse.com \
--to=jbeulich@suse.com \
--cc=George.Dunlap@eu.citrix.com \
--cc=JGross@suse.com \
--cc=andrew.cooper3@citrix.com \
--cc=dfaggioli@suse.com \
--cc=ian.jackson@citrix.com \
--cc=julien.grall@arm.com \
--cc=konrad.wilk@oracle.com \
--cc=mengxu@cis.upenn.edu \
--cc=roger.pau@citrix.com \
--cc=sstabellini@kernel.org \
--cc=tim@xen.org \
--cc=wl@xen.org \
--cc=xen-devel@lists.xenproject.org \
/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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.