From: Rik van Riel <riel@redhat.com>
To: Avi Kivity <avi@redhat.com>
Cc: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>,
Ingo Molnar <mingo@elte.hu>,
peterz@infradead.org, linux-kernel@vger.kernel.org,
vatsa@linux.vnet.ibm.com, bharata@linux.vnet.ibm.com
Subject: Re: [RFC PATCH 0/4] Gang scheduling in CFS
Date: Wed, 04 Jan 2012 15:56:49 -0500 [thread overview]
Message-ID: <4F04BD11.8090302@redhat.com> (raw)
In-Reply-To: <4F04898B.1080600@redhat.com>
On 01/04/2012 12:16 PM, Avi Kivity wrote:
> On 01/04/2012 06:47 PM, Rik van Riel wrote:
>>> So it looks like the default is optimal, at least wrt the cases you
>>> tested and your test workload.
>>
>>
>> It depends on the workload.
>>
>> I believe ebizzy synchronously bounces messages around between
>> userland threads, and may benefit from lower latency preemption
>> and re-scheduling.
>>
>> Workloads like AMQP do asynchronous messaging, and are likely
>> to benefit from having a lower number of switches.
>>
>> I do not know which kind of workload is more prevalent.
>>
>> Another worry with gang scheduling is scalability. One of
>> the reasons Linux scales well to larger systems is that a
>> lot of things are done CPU local, without communicating
>> things with other CPUs. Making the scheduling algorithm
>> system-global has the potential to add in a lot of overhead.
>>
>> Likewise, removing the ability to migrate workloads to idle
>> CPUs is likely to hurt a lot of real world workloads.
>>
>> Benchmarks don't care, because they run full-out. However,
>> users do not run benchmarks nearly as much as they run
>> actual workloads...
>>
>
> I think we can solve it at the guest level. The paravirt ticketlock
> stuff introduces wait/wake calls (actually wait is just a HLT
> instruction); we could spin for a while, then HLT until the other side
> wakes us. We should do this for all sites that busy wait.
Agreed, that would probably be the best (and nicest) solution.
--
All rights reversed
next prev parent reply other threads:[~2012-01-04 20:57 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-19 8:33 [RFC PATCH 0/4] Gang scheduling in CFS Nikunj A. Dadhania
2011-12-19 8:34 ` [RFC PATCH 1/4] sched: Adding cpu.gang file to cpu cgroup Nikunj A. Dadhania
2011-12-19 8:34 ` [RFC PATCH 2/4] sched: Adding gang scheduling infrastrucure Nikunj A. Dadhania
2011-12-19 15:51 ` Peter Zijlstra
2011-12-19 16:51 ` Peter Zijlstra
2011-12-20 1:43 ` Nikunj A Dadhania
2011-12-20 1:39 ` Nikunj A Dadhania
2011-12-19 8:34 ` [RFC PATCH 3/4] sched: Gang using set_next_buddy Nikunj A. Dadhania
2011-12-19 8:35 ` [RFC PATCH 4/4] sched:Implement set_gang_buddy Nikunj A. Dadhania
2011-12-19 15:51 ` Peter Zijlstra
2011-12-20 1:43 ` Nikunj A Dadhania
2011-12-26 2:30 ` Nikunj A Dadhania
2011-12-19 11:23 ` [RFC PATCH 0/4] Gang scheduling in CFS Ingo Molnar
2011-12-19 11:44 ` Avi Kivity
2011-12-19 11:50 ` Nikunj A Dadhania
2011-12-19 11:59 ` Avi Kivity
2011-12-19 12:06 ` Nikunj A Dadhania
2011-12-19 12:50 ` Avi Kivity
2011-12-19 13:09 ` Nikunj A Dadhania
2011-12-19 11:45 ` Nikunj A Dadhania
2011-12-19 13:22 ` Nikunj A Dadhania
2011-12-19 16:28 ` Ingo Molnar
2011-12-21 10:39 ` Nikunj A Dadhania
2011-12-21 10:43 ` Avi Kivity
2011-12-23 3:20 ` Nikunj A Dadhania
2011-12-23 10:36 ` Ingo Molnar
2011-12-25 10:58 ` Avi Kivity
2011-12-25 15:45 ` Avi Kivity
2011-12-26 3:14 ` Nikunj A Dadhania
2011-12-26 9:05 ` Avi Kivity
2011-12-26 11:33 ` Nikunj A Dadhania
2011-12-26 11:41 ` Avi Kivity
2011-12-27 1:47 ` Nikunj A Dadhania
2011-12-27 9:15 ` Avi Kivity
2011-12-27 10:24 ` Nikunj A Dadhania
2011-12-27 3:15 ` Nikunj A Dadhania
2011-12-27 9:17 ` Avi Kivity
2011-12-27 9:44 ` Nikunj A Dadhania
2011-12-27 9:51 ` Avi Kivity
2011-12-27 10:10 ` Nikunj A Dadhania
2011-12-27 10:34 ` Avi Kivity
2011-12-27 10:43 ` Nikunj A Dadhania
2011-12-27 10:53 ` Avi Kivity
2011-12-30 9:51 ` Ingo Molnar
2011-12-30 10:10 ` Nikunj A Dadhania
2011-12-31 2:21 ` Nikunj A Dadhania
2012-01-02 4:20 ` Nikunj A Dadhania
2012-01-02 9:39 ` Avi Kivity
2012-01-02 10:22 ` Nikunj A Dadhania
2012-01-02 9:37 ` Avi Kivity
2012-01-02 10:30 ` Nikunj A Dadhania
2012-01-02 13:33 ` Avi Kivity
2012-01-04 10:52 ` Nikunj A Dadhania
2012-01-04 14:41 ` Avi Kivity
2012-01-04 14:56 ` Srivatsa Vaddagiri
2012-01-04 17:13 ` Avi Kivity
2012-01-05 6:57 ` Nikunj A Dadhania
2012-01-04 16:47 ` Rik van Riel
2012-01-04 17:16 ` Avi Kivity
2012-01-04 20:56 ` Rik van Riel [this message]
2012-01-04 21:31 ` Peter Zijlstra
2012-01-04 21:41 ` Avi Kivity
2012-01-05 9:10 ` Ingo Molnar
2012-02-20 8:08 ` Nikunj A Dadhania
2012-02-20 8:14 ` Ingo Molnar
2012-02-20 10:51 ` Peter Zijlstra
2012-02-20 11:53 ` Nikunj A Dadhania
2012-02-20 12:02 ` Srivatsa Vaddagiri
2012-02-20 12:14 ` Peter Zijlstra
2012-01-05 2:10 ` Nikunj A Dadhania
2011-12-19 15:51 ` Peter Zijlstra
2011-12-19 16:09 ` Alan Cox
2011-12-19 22:10 ` Benjamin Herrenschmidt
2011-12-20 1:56 ` Nikunj A Dadhania
2011-12-20 8:52 ` Jeremy Fitzhardinge
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=4F04BD11.8090302@redhat.com \
--to=riel@redhat.com \
--cc=avi@redhat.com \
--cc=bharata@linux.vnet.ibm.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=nikunj@linux.vnet.ibm.com \
--cc=peterz@infradead.org \
--cc=vatsa@linux.vnet.ibm.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).