linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Nick Piggin <piggin@cyberone.com.au>
To: markw@osdl.org
Cc: linux-kernel@vger.kernel.org, osdldbt-general@lists.sourceforge.net
Subject: Re: hyperthreading performance with dbt-2 on 2.6.0-test11
Date: Tue, 09 Dec 2003 11:17:26 +1100	[thread overview]
Message-ID: <3FD51496.5000500@cyberone.com.au> (raw)
In-Reply-To: <200312082354.hB8NsqZ17359@mail.osdl.org>

[-- Attachment #1: Type: text/plain, Size: 1488 bytes --]



markw@osdl.org wrote:

>Hello, I have some data with hyperthreading I wanted to share.
>
>I've seen about a 15% performance decrease in performance on a 4-way
>Xeon system when I enable hyperthreading for my DBT-2 workload.  I also
>gave Ingo's test11-C1 patch that someone pointed me to a try and only
>saw a 12% decrease. Has anyone found this to be common with any specific
>workloads?
>
>I'm not really sure what to look for, but I do see some changes in the
>readprofile data, which I've copied in part below.  It appears that the
>count of schedule, __make_request, and try_to_wake_up are the only
>functions at the top of the profile that are significantly different.
>The links I have posted also have pointers to oprofile data as well as
>annotated assembly source output, if that interests anyone.  If I can
>provide any other details, let me know.
>

Hi Mark,
It could be cache contention which I think is typically the reason
hyperthreading can hurt performance. Its basically impossible for
the scheduler to correct this automatically (access to performance
counters might make it slightly less impossible).

Probably the CPU hotplug interface would enable a tool to effectively
turn HT on or off and it would be up to an administrator to tune
performance.

You could try my scheduler patchset if you like. I have recently got
HT support working (its against test11, you need to turn CONFIG_SMT
on), although if Ingo's patch doesn't help much, mine probably won't
either.


[-- Attachment #2: w26p21.gz --]
[-- Type: application/x-tar, Size: 13256 bytes --]

  reply	other threads:[~2003-12-09  0:59 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2003-12-08 23:54 hyperthreading performance with dbt-2 on 2.6.0-test11 markw
2003-12-09  0:17 ` Nick Piggin [this message]
2003-12-09  3:12   ` Mark Wong
2003-12-09  3:27     ` Nick Piggin
2003-12-09  3:37       ` Mark Wong

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=3FD51496.5000500@cyberone.com.au \
    --to=piggin@cyberone.com.au \
    --cc=linux-kernel@vger.kernel.org \
    --cc=markw@osdl.org \
    --cc=osdldbt-general@lists.sourceforge.net \
    /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).