From: Holger Wolf <wolf@linux.vnet.ibm.com>
To: Arjan van de Ven <arjan@infradead.org>
Cc: Holger.Wolf@de.ibm.com, mingo@elte.hu, schwidefsky@de.ibm.com,
linux-kernel@vger.kernel.org
Subject: Re: Scheduler behaviour
Date: Fri, 07 Dec 2007 17:29:44 +0100 [thread overview]
Message-ID: <475974F8.9040603@linux.vnet.ibm.com> (raw)
In-Reply-To: <20071205132631.79940bd5@laptopd505.fenrus.org>
Arjan van de Ven wrote:
> On Wed, 05 Dec 2007 21:15:30 +0100
> Holger Wolf <wolf@linux.vnet.ibm.com> wrote:
>
>
>> We discovered performance degradation with dbench when using kernel
>> 2.6.23 compared to kernel 2.6.22.
>>
>> In our case we booted a Linux in a IBM System z9 LPAR with 256MB of
>> ram with 4 CPU's. This system uses a striped LV with 16 disks on a
>> Storage Server connected via 8 4GBit links.
>> A dbench was started on that system performing I/O operations on the
>> striped LV. dbench runs were performed with 1 to 62 processes.
>> Measurements with a 2.6.22 kernel were compared to measurements with
>> a 2.6.23 kernel. We saw a throughput degradation from 7.2 to 23.4
>>
>
> this is good news!
> dbench rewards unfair behavior... so higher dbench usually means a
> worse kernel ;)
>
>
>
tests with 2.6.22 including CFS show the same results.
This means the pressure on page cache is much higher when all processes
run in parallel.
We see this behavior as well with iozone when writing on many disks with
many threads and just 256 MB memory.
This means the scheduler schedules as it should - fair.
regards Holger
prev parent reply other threads:[~2007-12-07 16:30 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-05 20:15 Scheduler behaviour Holger Wolf
2007-12-05 21:15 ` Peter Zijlstra
2007-12-05 21:21 ` Ingo Molnar
2007-12-05 21:26 ` Arjan van de Ven
2007-12-06 21:53 ` Jarek Poplawski
2007-12-07 16:29 ` Holger Wolf [this message]
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=475974F8.9040603@linux.vnet.ibm.com \
--to=wolf@linux.vnet.ibm.com \
--cc=Holger.Wolf@de.ibm.com \
--cc=arjan@infradead.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@elte.hu \
--cc=schwidefsky@de.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).