linux-kernel - Re: [PATCH 15/18] fs: introduce a per-cpu last

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Message-ID: <87d3rl5c1h.fsf@basil.nowhere.org>
Date:	Fri, 08 Oct 2010 10:22:34 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Dave Chinner <david@...morbit.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/18] fs: introduce a per-cpu last_ino allocator

Dave Chinner <david@...morbit.com> writes:

> From: Eric Dumazet <eric.dumazet@...il.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.

Acked-by: Andi Kleen <ak@...ux.intel.com>

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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