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    SubjectRe: [PATCH 15/18] fs: introduce a per-cpu last_ino allocator
    On Fri, Oct 08, 2010 at 10:22:34AM +0200, Andi Kleen wrote:
    > Dave Chinner <david@fromorbit.com> writes:
    >
    > > From: Eric Dumazet <eric.dumazet@gmail.com>
    > >
    > > new_inode() dirties a contended cache line to get increasing
    > > inode numbers. This limits performance on workloads that cause
    > > significant parallel inode allocation.
    > >
    > > Solve this problem by using a per_cpu variable fed by the shared
    > > last_ino in batches of 1024 allocations. This reduces contention on
    > > the shared last_ino, and give same spreading ino numbers than before
    > > (i.e. same wraparound after 2^32 allocations).
    >
    > This doesn't help for Unix disk file systems, so not fully sure why you
    > need it for XFS.
    >
    > But looks reasonable, although it would be better to simply fix
    > sockets/pipes/etc. to not allocate an inode numbers.

    Can be done if you bother to add ->getattr() for those, but you'll need
    to do some kind of lazy allocation of inumbers for those; fstat() _will_
    want st_ino.


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