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Re: [PATCH 3/4] xfs: allow assigning the tail lsn with the AIL lock held

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH 3/4] xfs: allow assigning the tail lsn with the AIL lock held
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 22 Mar 2012 10:29:56 +1100
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20120316175636.373605151@xxxxxxxxxxxxxxxxxxxxxx>
References: <20120316175541.258282540@xxxxxxxxxxxxxxxxxxxxxx> <20120316175636.373605151@xxxxxxxxxxxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Fri, Mar 16, 2012 at 01:55:44PM -0400, Christoph Hellwig wrote:
> Provide a variant of xlog_assign_tail_lsn that has the AIL lock already
> held.  By doing so we do an additional atomic_read + atomic_set under
> the lock, which comes down to two instructions.
> 
> Switch xfs_trans_ail_update_bulk and xfs_trans_ail_delete_bulk to the
> new version to reduce the number of lock roundtrips, and prepare for
> a new addition that would require a third lock roundtrip in
> xfs_trans_ail_delete_bulk.

What new addition is that? I don't see it in this patchset (maybe
I'm just blind), so maybe this isn't necessary in the commit
message?


Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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