Weblog entry #2 for neofpo
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I recently used Windows Vista and it has a very nice feacure: a top like disk access statistics. I can easily identify what process is using the disk and at what rate. I could manage to easily solve some performance issues on Vista using this tool.
The question is: is there a way Linux kernel export disk access usage per process? All I have seen until now is a system wide value, for a whole block device...
There is the brute force method of course, lsof + find by latest modification / access date... but that's not exactly what I want.
Ah, I know about laptop mode, but I wish to fix the cause of the problem (no more useless disk access).
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Also, there's no reason that one couldn't produce this information in principle, is there? What pieces are missing to getting this info? Is there a kernel interface reporting issue? Is /proc not providing statistics that it should? Are we missing a userland tool that reads and reports on the contents of /proc in a human-readable fashion? Or is there actually some reason that each physical disk access can't be legitimately associated with a single process?
The clearer the problem is, the better shot we have of solving it. I'd very much like to be able to do what neofpo is suggesting.
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Saturday June 9th, 2007Version 7.1.5 doesn't appear to be in debian yet (and you'd need to be running the kernel from sid anyway):Sysstat 7.1.5 released (development version).
At last, this version includes a long awaited feature: per-process I/O statistics, that you can now display with the command pidstat and its new option -d. Of course, you will need a recent Linux kernel for that (2.6.20+).
[0 dkg@squeak ~]$ apt-cache policy sysstat
sysstat:
Installed: 7.1.4-1
Candidate: 7.1.4-1
Version table:
*** 7.1.4-1 0
500 http://ftp.debian.org testing/main Packages
200 http://ftp.debian.org unstable/main Packages
100 /var/lib/dpkg/status
[0 dkg@squeak ~]$ But if you are running the latest kernel, you should try building the new package. Report back when you get a chance! You might also want to file a wishlist bug against debian's sysstat package, asking for the new version.
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I will check this feature on the next days, hope top incorporate it.
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It built for me with no errors at all:
[0 dkg@squeak ~]$ mkdir -p src/sysstat [0 dkg@squeak ~]$ cd src/sysstat [0 dkg@squeak sysstat]$ apt-get source sysstat Reading package lists... Done Building dependency tree... Done Need to get 234kB of source archives. Get:1 http://ftp.debian.org testing/main sysstat 7.1.4-1 (dsc) [578B] Get:2 http://ftp.debian.org testing/main sysstat 7.1.4-1 (tar) [208kB] Get:3 http://ftp.debian.org testing/main sysstat 7.1.4-1 (diff) [25.4kB] Fetched 234kB in 1s (118kB/s) dpkg-source: extracting sysstat in sysstat-7.1.4 dpkg-source: unpacking sysstat_7.1.4.orig.tar.gz dpkg-source: applying ./sysstat_7.1.4-1.diff.gz [0 dkg@squeak sysstat]$ (cd sysstat-7.1.4/ && uscan) sysstat: Newer version (7.1.5) available on remote site: http://perso.orange.fr/sebastien.godard/sysstat-7.1.5.tar.gz (local version is 7.1.4) sysstat: Successfully downloaded updated package sysstat-7.1.5.tar.gz and symlinked sysstat_7.1.5.orig.tar.gz to it [1 dkg@squeak sysstat]$ tar xzf sysstat-7.1.5.tar.gz [0 dkg@squeak sysstat]$ cd sysstat-7.1.5 [0 dkg@squeak sysstat-7.1.5]$ zcat ../sysstat_7.1.4-1.diff.gz | patch -s -p1 [0 dkg@squeak sysstat-7.1.5]$ debuild -uc -usand when debuild finished running, i had the new package available, which i could put online. If you're not running i386, you could probably do the same steps on your architecture to get a native package yourself. debuild and uscan are in the devscripts package, so other than that and build-essential, you'll only need to make sure you can satisfy the build-deps for sysstat:
[0 dkg@squeak sysstat]$ grep ^Build-Depends: sysstat-7.1.4/debian/control Build-Depends: debhelper (>= 5.0.7), gettext [0 dkg@squeak sysstat]$Please let me know if it works for you, because i've often wanted this feature myself. It might even be worth playing with the unstable kernel.
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I follow the instructions below to patch my kernel:
* http://www.atconsultancy.nl/atop/kernpatch.html
And to build a kernel package:
* http://www.debian.org/releases/stable/i386/ch08s06.html.en
Once you're running the new kernel, the atop utility (available from apt) has a disk mode to show you per-process disk accesses.
--
Darren Paul Griffith
www.madphilosopher.ca
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hdparm -B 255 /dev/hda
in /etc/rc.local
There may have been something added to call /etc/rc.local
This stops the disk spinning down every second or so which just can't be good.
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I still had no time to test this new feature to identify I/O by process. Think I will be able to do this at this weekend.
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