Re: Very low disk performance on 5.x (some tweaking and more results)

From: Steven Hartland (killing_at_multiplay.co.uk)
Date: 05/04/05

  • Next message: Mike Tancsa: "Re: Very low disk performance on 5.x (some tweaking and more results)" 
    To: "Poul-Henning Kamp" <phk@phk.freebsd.dk>, "Mike Tancsa" <mike@sentex.net>
Date: Wed, 4 May 2005 15:04:15 +0100

    Did you also try the sys/param.h change that helped here.
    Also when testing on FS I found bs=1024k to degrade performance
    try with 64k.
    Is this a raid volume? If so on my setup anything other that a 16k stripe
    and performance went out the window.

    For the 'time' its easier to understand if u use:
    /usr/bin/time -h

    Last but not least. I found some very strange behaviour late last night.
    If I created the raid set but didnt power down after doing so the
    results where a lot lower than when I did. Dont ask me why I have
    no idea, only noticed as I retested a result after I installed a new
    fan in the machine and was totally a los

    My initial starting results where:
    Write: 140Mb/s
    Read: 49Mb/s

    My current values are:
    Write: 140Mb/s
    Read: 195Mb/s

    Changes made:
    1. 16k RAID5 stripe not 64k ( default )
    2. vfs.read_max=16
    3. MAXPHYS = 256 ( was 128 )
    4. newfs /dev/da0 ( was a basic install with multi partitions )

    I'm currently seeing some VERY strange behaviour which could
    be the RAID controller negotiating different PCI-X speeds.

    Anyone know how to check the state of a PCI-X card?

    Power up, login:
    dd if=/dev/da0 of=/dev/null bs=64k count=100000
    100000+0 records in
    100000+0 records out
    6553600000 bytes transferred in 42.997295 secs (152418891 bytes/sec)
    mount /dev/da0 /mnt
    dd if=/mnt/testfile of=/dev/null bs=64k count=100000
    100000+0 records in
    100000+0 records out
    6553600000 bytes transferred in 48.757091 secs (134413270 bytes/sec)
    shutdown -p now

    Power up, login:
    dd if=/dev/da0 of=/dev/null bs=64k count=100000
    100000+0 records in
    100000+0 records out
    6553600000 bytes transferred in 28.365671 secs (231039838 bytes/sec)
    mount /dev/da0 /mnt
    dd if=/mnt/testfile of=/dev/null bs=64k count=100000
    100000+0 records in
    100000+0 records out
    6553600000 bytes transferred in 32.012170 secs (204722143 bytes/sec)

        Steve
    ----- Original Message -----
    From: "Mike Tancsa" <mike@sentex.net>
    > OK, some further tests, trying to control for this. I am not sure what
    > values to actually fiddle with via bsdlable as this is the entire disk so I
    > will just vary mounting da0 vs da0s1d. I also cvsup'd to current as of
    > yesterday (FreeBSD nfs.sentex.ca 6.0-CURRENT FreeBSD 6.0-CURRENT #0: Mon
    > May 2 15:03:53 EDT 2005). I will also try with Scott's changes to the
    > driver which went in after.
    >
    > Also, the newfs params does seem to make a very big difference and
    > vfs.read_max as well.
    ....

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