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Date: Fri, 8 Oct 2010 10:56:58 +0100
From: Al Viro <viro@ZenIV.linux.org.uk>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 15/18] fs: introduce a per-cpu last_ino allocator
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On Fri, Oct 08, 2010 at 04:21:29PM +1100, Dave Chinner wrote:
> 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).

FWIW, that one is begging to be split; what I mean is that there are
two classes of callers; ones that will set i_ino themselves anyway
and ones that really want i_ino invented.  Two functions?