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Re: [PATCH 2/5] xfs: do not immediately reuse busy extent ranges

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Subject: Re: [PATCH 2/5] xfs: do not immediately reuse busy extent ranges
From: Alex Elder <aelder@xxxxxxx>
Date: Tue, 29 Mar 2011 14:04:16 -0500
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20110328210914.791205854@xxxxxxxxxxxxxxxxxxxxxx>
References: <20110328210614.832613417@xxxxxxxxxxxxxxxxxxxxxx> <20110328210914.791205854@xxxxxxxxxxxxxxxxxxxxxx>
Reply-to: aelder@xxxxxxx
On Mon, 2011-03-28 at 17:06 -0400, Christoph Hellwig wrote:
> Every time we reallocate a busy extent, we cause a synchronous log force
> to occur to ensure the freeing transaction is on disk before we continue
> and use the newly allocated extent.  This is extremely sub-optimal as we
> have to mark every transaction with blocks that get reused as synchronous.
> 
> Instead of searching the busy extent list after deciding on the extent to
> allocate, check each candidate extent during the allocation decisions as
> to whether they are in the busy list.  If they are in the busy list, we
> trim the busy range out of the extent we have found and determine if that
> trimmed range is still OK for allocation. In many cases, this check can
> be incorporated into the allocation extent alignment code which already
> does trimming of the found extent before determining if it is a valid
> candidate for allocation.
> 
> Based on two earlier patches from Dave Chinner.
> 
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>

Looks good.

Reviewed-by: Alex Elder <aelder@xxxxxxx>


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