From: "Gordon Mckeown" <ml_lkml@thefluffyone.net>
To: LKML <linux-kernel@vger.kernel.org>
Cc: "Tomasz Chmielewski" <mangoo@wpkg.org>
Subject: Re: Very high IOWait during all disk activity
Date: Fri, 29 Feb 2008 15:47:08 +0000 [thread overview]
Message-ID: <74d8fc520802290747o2c97992ar7af2b8c295fe2fb2@mail.gmail.com> (raw)
In-Reply-To: <47C82244.60307@wpkg.org>
On Fri, Feb 29, 2008 at 3:18 PM, Tomasz Chmielewski <mangoo@wpkg.org> wrote:
> Unless you can write to the disk faster than fetch data from /dev/zero -
> yes, it is normal.
OK, thank you; it has been a struggle to get confirmation of this;
perhaps because the way IOWait is measured has changed at some point?
> Try running:
>
> cat /dev/zero | bzip2 -c >/dev/null
>
> when your IOwait is big (because you write a big file), and then watch
> the numbers.
Ah, I can see that the CPU-intensive command soaks up the cycles that
would otherwise have been reported as IOWaits.
Unfortunately this doesn't help explain why Windows XP on the same box
can complete an "identical" copy operation in half the time. Perhaps
it's just due to the different filesystems, or the way write caching
works?
Thanks,
Gordon.
next prev parent reply other threads:[~2008-02-29 15:47 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-02-29 15:18 Very high IOWait during all disk activity Tomasz Chmielewski
2008-02-29 15:47 ` Gordon Mckeown [this message]
2008-02-29 16:00 ` Tomasz Chmielewski
2008-03-01 13:31 ` Gordon Mckeown
2008-03-01 19:41 ` Gordon Mckeown
-- strict thread matches above, loose matches on Subject: below --
2008-02-29 14:16 Gordon Mckeown
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=74d8fc520802290747o2c97992ar7af2b8c295fe2fb2@mail.gmail.com \
--to=ml_lkml@thefluffyone.net \
--cc=linux-kernel@vger.kernel.org \
--cc=mangoo@wpkg.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 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).