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    SubjectRe: huge improvement with per-device dirty throttling

    --- Martin Knoblauch <knobi@knobisoft.de> wrote:

    >
    > --- Leroy van Logchem <leroy.vanlogchem@wldelft.nl> wrote:
    >
    > > Andrea Arcangeli wrote:
    > > > On Wed, Aug 22, 2007 at 01:05:13PM +0200, Andi Kleen wrote:
    > > >> Ok perhaps the new adaptive dirty limits helps your single disk
    > > >> a lot too. But your improvements seem to be more "collateral
    > > damage" @)
    > > >>
    > > >> But if that was true it might be enough to just change the dirty
    > > limits
    > > >> to get the same effect on your system. You might want to play
    > with
    > > >> /proc/sys/vm/dirty_*
    > > >
    > > > The adaptive dirty limit is per task so it can't be reproduced
    > with
    > > > global sysctl. It made quite some difference when I researched
    > into
    > > it
    > > > in function of time. This isn't in function of time but it
    > > certainly
    > > > makes a lot of difference too, actually it's the most important
    > > part
    > > > of the patchset for most people, the rest is for the corner cases
    > > that
    > > > aren't handled right currently (writing to a slow device with
    > > > writeback cache has always been hanging the whole thing).
    > >
    > >
    > > Self-tuning > static sysctl's. The last years we needed to use very
    >
    > > small values for dirty_ratio and dirty_background_ratio to soften
    > the
    > >
    > > latency problems we have during sustained writes. Imo these patches
    >
    > > really help in many cases, please commit to mainline.
    > >
    > > --
    > > Leroy
    > >
    >
    > while it helps in some situations, I did some tests today with
    > 2.6.22.6+bdi-v9 (Peter was so kind) which seem to indicate that it
    > hurts NFS writes. Anyone seen similar effects?
    >
    > Otherwise I would just second your request. It definitely helps the
    > problematic performance of my CCISS based RAID5 volume.
    >

    please disregard my comment about NFS write performance. What I have
    seen is caused by some other stuff I am toying with.

    So, I second your request to push this forward.

    Martin

    ------------------------------------------------------
    Martin Knoblauch
    email: k n o b i AT knobisoft DOT de
    www: http://www.knobisoft.de
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