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    SubjectRe: VFS scalability git tree
    On Tue, Jul 27, 2010 at 05:05:39PM +1000, Nick Piggin wrote:
    > On Fri, Jul 23, 2010 at 11:55:14PM +1000, Dave Chinner wrote:
    > > On Fri, Jul 23, 2010 at 05:01:00AM +1000, Nick Piggin wrote:
    > > > I'm pleased to announce I have a git tree up of my vfs scalability work.
    > > >
    > > > git://git.kernel.org/pub/scm/linux/kernel/git/npiggin/linux-npiggin.git
    > > > http://git.kernel.org/?p=linux/kernel/git/npiggin/linux-npiggin.git
    > > >
    > > > Branch vfs-scale-working
    > >
    > > With a production build (i.e. no lockdep, no xfs debug), I'll
    > > run the same fs_mark parallel create/unlink workload to show
    > > scalability as I ran here:
    > >
    > > http://oss.sgi.com/archives/xfs/2010-05/msg00329.html
    >
    > I've made a similar setup, 2s8c machine, but using 2GB ramdisk instead
    > of a real disk (I don't have easy access to a good disk setup ATM, but
    > I guess we're more interested in code above the block layer anyway).
    >
    > Made an XFS on /dev/ram0 with 16 ags, 64MB log, otherwise same config as
    > yours.

    I also tried dbench on this setup. 20 runs of dbench -t20 8
    (that is a 20 second run, 8 clients).

    Numbers are throughput, higher is better:

    N Min Max Median Avg Stddev
    vanilla 20 2219.19 2249.43 2230.43 2230.9915 7.2528893
    scale 20 2428.21 2490.8 2437.86 2444.111 16.668256
    Difference at 95.0% confidence
    213.119 +/- 8.22695
    9.55268% +/- 0.368757%
    (Student's t, pooled s = 12.8537)

    vfs-scale is 9.5% or 210MB/s faster than vanilla.

    Like fs_mark, dbench has creat/unlink activity, so I hope rcu-inodes
    should not be such a problem in practice. In my creat/unlink benchmark,
    it is creating and destroying one inode repeatedly, which is the
    absolute worst case for rcu-inodes. Wheras in most real workloads
    would be creating and destroying many inodes, which is not such a dis
    advantage for rcu-inodes.

    Incidentally, XFS was by far the fastest "real" filesystem I tested on
    this workload. ext4 was around 1700MB/s (ext2 was around 3100MB/s and
    ramfs is 3350MB/s).



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