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Date:	Wed, 21 Jan 2009 06:52:16 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Mike Waychison <mikew@...gle.com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v1 0/8] Deferred dput() and iput() -- reducing lock contention

Mike Waychison <mikew@...gle.com> writes:

> livelock on dcache_lock/inode_lock (specifically in atomic_dec_and_lock()) 

I'm not sure how something can livelock in atomic_dec_and_lock which
doesn't take a spinlock itself? Are you saying you run into NUMA memory
unfairness here? Or did I misparse you?

> This patchset is an attempt to try and reduce the locking overheads associated
> with final dput() and final iput().  This is done by batching dentries and
> inodes into per-process queues and processing them in 'parallel' to consolidate
> some of the locking.

I was wondering what this does to the latencies when dput/iput
is only done for very objects. Does it increase costs then
significantly?

As a high level comment it seems like a lot of work to work
around global locks, like the inode_lock, where it might be better to 
just split the lock up? Mind you I don't have a clear proposal
how to do that, but surely it's doable somehow.

-Andi

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