Re[2]: slow tar performance on fbsd5

From: JG (jarek_at_adeon.lublin.pl)
Date: 08/24/05

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    Date: Wed, 24 Aug 2005 23:00:23 +0200
To: Jonathan Noack <noackjr@alumni.rice.edu>

    > Will noatime make a difference when unpacking a tar archive (assuming an
    > otherwise idle system, at least)? My understanding of atime is that it
    > might slow down the disk for later accesses due to atime writes, but
    > when creating files it shouldn't have any effect. Is that not correct?

    Yes, you're right.

    > Your other settings appear ok, but I'd turn off hyperthreading. Almost
    > every FreeBSD/HT test has shown that it reduces performance because the
    > scheduler is not HT-aware. When the system is relatively idle (single
    > dd running, for example), it might not pessimize things, but it will
    > most likely slow you down under load.

    HTT is a big performance hit for me, mainly for webserver. I've much worse diskinfo
    results without HTT, don't know why. Tar is upacking a bit longer with HTT disabled.

    > This sounds like you're running into the old "lemming syncer" problem.
    > There is currently some work on disk schedulers (even a Summer of Code
    > project), but it will most likely not make it into 5.x.

    Agrh..

    Regards,
    Jarek

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