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

[Andi Kleen]

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@xxxxxxxxxxxxx> writes:
> > 
> > > From: Eric Dumazet <eric.dumazet@xxxxxxxxx>
> > >
> > > 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@xxxxxxxxxxxxxxx -- Speaking for myself only.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/