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Re: [PATCH 2/2] xfs: stop using kmalloc in xfs_buf_get_noaddr

To: Michael Nishimoto <miken@xxxxxxxxx>
Subject: Re: [PATCH 2/2] xfs: stop using kmalloc in xfs_buf_get_noaddr
From: Christoph Hellwig <hch@xxxxxx>
Date: Wed, 7 Mar 2007 18:15:47 +0100
Cc: Christoph Hellwig <hch@xxxxxx>, xfs@xxxxxxxxxxx, ecashin@xxxxxxxxxx, akpm@xxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
In-reply-to: <45EEF0B5.40905@agami.com>
References: <20070307101324.GC30587@lst.de> <45EEF0B5.40905@agami.com>
Sender: xfs-bounce@xxxxxxxxxxx
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On Wed, Mar 07, 2007 at 09:04:53AM -0800, Michael Nishimoto wrote:
> Incore log buffers are not always a power of two of the page size.
> In particular, when xfs is running over software raid devices, the
> log buffers are allocated to match the size of a stripe.
> 
> However, they are always a multiple of PAGE_SIZE, so we are still safe.

It's not actually about beeing safe - any allocation is still safe
with this patch.  The issue is just that we waste memory because
we round up allocations to the next page size.

The power of two bit is actually wrong in this mail, it was about
another optimization I have that needs some more testing first.


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