Re: FreeBSD 5.3 I/O Performance / Linux 2.6.10 | Continued Discussion

From: Nick Pavlica (linicks_at_gmail.com)
Date: 01/28/05

  • Next message: Robert Watson: "Re: FreeBSD 5.3 I/O Performance / Linux 2.6.10 | Continued Discussion" 
    Date: Thu, 27 Jan 2005 18:04:31 -0700
To: Robert Watson <rwatson@freebsd.org>

    > The move to an MPSAFE VFS will help with that a lot, I should think.

    Do you know if this will find it's way to 5.x in the near future?

    >
    > Also, while on face value this may seem odd, could you try the following
    > additional variables:
    >
    > - Layer the test UFS partition directly over ad0 instead of ad0s1a
    > - UFS1 vs UFS2

    I just tested with UFS1 and had almost the exact same results.

    >
    > Finally, in as much as is possible, make sure that the layout of the disks
    > is approximately the same -- as countless benchmarking papers show, there
    > are substantial differences (10%+) in I/O throughput depending on where on
    > the disk surface operations occur. That's one of the reasons to try UFS1
    > for the test partition, although not the only one.

    My tests use the exact same disk layout, and hardware. However, I
    have had consistent results on all 4 boxes that I have tested on.

    At this point I'm making the assumption that the poor disk I/O
    performance on 5.3 isn't a file system issue, but is tied to a larger
    issue with the Kernel (I know never make assumptions ... :)). In all
    my testing, I have noticed that 5.3 doesn't appear to release cpu
    resources even if there isn't any other demand for resources. I would
    compare it to driveling a car with a governor on it. When I tested
    with 4.11, it allocated considerably more resources. I do hope that
    the 5.x issues are resolved soon so that I can deploy may production
    servers on it rather than starting on 4 and them making the big
    switch. I will probably test 6 for the fun of it.

    Thanks!
    --Nick Pavlica
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  • Next message: Robert Watson: "Re: FreeBSD 5.3 I/O Performance / Linux 2.6.10 | Continued Discussion"

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