Messages in this thread | | | From | Thomas Fjellstrom <> | Subject | Re: Poor desktop responsiveness with background I/O-operations | Date | Sat, 19 Sep 2009 22:11:17 -0600 |
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On Sat September 19 2009, Ulrich Lukas wrote: > Hi, > > > using a recent hard-/software setup, I observed that continuous > read/write operations severely degrade the overall system responsiveness > in typical desktop-PC use cases. > > Merely doing write/read operations on a data volume leads to stuck text > and mouse cursors, seconds-long delays for simple window-context > switches in X11, dropouts in low-resolution video playback etc. > > > > Test case: > - 64-bit dual-core PC, SATA harddrive, plenty of free RAM > - vanilla Linux 2.6.31, Kubuntu 9.10 packages, all software 64-bit > > > How to reproduce: > - start KDE/GNOME-session > - open a terminal window and do as a non-root user: > dd if=/dev/zero of=/home/john-doe/testfile > (or dd if=/home/john-doe/big-testfile of=/dev/null) > > - a real use scenario would be a daily disk-backup or the > simple extraction of a tarball containing slightly bigger files > > > Observation: > - The system becomes _really_ slow as described above; unusable for > any multimedia tasks. > > - Using an encrypted (dm-crypt/LUKS) /home (e.g. on mobile computers) > compounds the issue to a painful extent. > > > > Possible culprits (I'm guessing) are the Linux I/O- or CPU scheduler. > > I realize that a single heavyweight transfer slows down I/O for the > corresponding transactions/processes/volumes etc. > > But there needs to be a fair distribution of I/O or CPU time which > leaves enough for other basic operations. And this doesn't seem to be > the case with recent Linux versions. > > > > > On a side note, I've tried the BFS-patches (bfs-221 on 2.6.31): This > yields significantly higher throughput when using disk encryption (50% > improvement with dm-crypt/LUKS, 512 bit aes-xts-plain cipher mode). But > with these patches, the responsiveness was even worse during my quick > test. Switching to a text-mode console: several /minutes/ delay... > > > I'm attaching my .config for linux 2.6.31 (grep ^C and bzip2-ed) >
I've seen similar things with my Intel p35 (q6600) system, especially under 64bit. Heavy i/o makes the rest of the system perform very badly. I have however not noticed nearly as much of a problem with my AMD (SB700&SB750) systems.
-- Thomas Fjellstrom tfjellstrom@shaw.ca
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