LKML Archive on
help / color / mirror / Atom feed
From: Asbjorn Sannes <>
To: Linux Kernel Mailing List <>
Subject: Unpredictable performance
Date: Fri, 25 Jan 2008 12:32:56 +0100	[thread overview]
Message-ID: <> (raw)


I am experiencing unpredictable results with the following test
without other processes running (exception is udev, I believe):
cd /usr/src/test
tar -jxf ../linux-
cp ../working-config linux-
cd linux-
make oldconfig
time make -j3 > /dev/null # This is what I note down as a "test" result
cd /usr/src ; umount /usr/src/test ; mkfs.ext3 /dev/cc/test
and then reboot

The kernel is booted with the parameter mem=81920000

For the results vary from (real time) 33m30.551s to 45m32.703s
(30 runs)
For with nop i/o scheduler from 29m8.827s to 55m36.744s (24 runs)
For also varied a lot.. but, lost results :(
For only vary from 34m32.054s to 38m1.928s (10 runs)

Any idea of what can cause this? I have tried to make the runs as equal
as possible, rebooting between each run.. i/o scheduler is cfq as default.

sys and user time only varies a couple of seconds.. and the order of
when it is "fast" and when it is "slow" is completly random, but it
seems that the results are mostly concentrated around the mean.

Asbjørn Sannes

             reply	other threads:[~2008-01-25 12:00 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-01-25 11:32 Asbjorn Sannes [this message]
2008-01-25 14:00 ` Nick Piggin
2008-01-25 14:31   ` Asbjørn Sannes
2008-01-25 15:03     ` Asbjørn Sannes
2008-01-26  0:38       ` Nick Piggin
2008-01-28  9:12         ` Asbjørn Sannes
2008-01-25 17:16 ` Ray Lee
2008-01-25 20:49   ` Asbjørn Sannes
     [not found]     ` <>
2008-01-28  9:02       ` Asbjørn Sannes

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:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \
    --subject='Re: Unpredictable performance' \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

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).