Re: [PATCH 15/18] fs: introduce a per-cpu last_ino allocator

Andi Kleen
2010-10-08T10:09:50Z

On Fri, Oct 08, 2010 at 10:58:24AM +0100, Al Viro wrote:
> 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.

Why not just put 0 in st_ino for sockets/pipes/etc. ?

-Andi
--
ak@linux.intel.com -- Speaking for myself only.