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From: Brian Foster <bfoster@redhat.com>
To: Dave Chinner <david@fromorbit.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 04/27] xfs: don't use speculative prealloc for small files
Date: Wed, 12 Jun 2013 12:10:00 -0400	[thread overview]
Message-ID: <51B89D58.80108@redhat.com> (raw)
In-Reply-To: <1371032567-21772-5-git-send-email-david@fromorbit.com>

On 06/12/2013 06:22 AM, Dave Chinner wrote:
> From: Dave Chinner <dchinner@redhat.com>
> 
...
> ---
>  fs/xfs/xfs_iomap.c |   13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index 8f8aaee..14be676 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -284,6 +284,15 @@ xfs_iomap_eof_want_preallocate(
>  		return 0;
>  
>  	/*
> +	 * If the file is smaller than the minimum prealloc and we are using
> +	 * dynamic preallocation, don't do any preallocation at all as it is
> +	 * likely this is the only write to the file that is going to be done.
> +	 */
> +	if (!(mp->m_flags & XFS_MOUNT_DFLT_IOSIZE) &&
> +	    XFS_ISIZE(ip) < mp->m_writeio_blocks)
> +		return 0;
> +

I stuck this on a box, got a 64k prealloc on an 8k file and then noticed
this was comparing inode size against a block count. This should
probably be:

	XFS_ISIZE(ip) < XFS_FSB_TO_B(mp, mp->m_writeio_blocks)

Given that, we avoid preallocs entirely until the file size reaches the
minimum write size (assuming dynamic prealloc mode).

> +	/*
>  	 * If there are any real blocks past eof, then don't
>  	 * do any speculative allocation.
>  	 */
> @@ -345,6 +354,10 @@ xfs_iomap_eof_prealloc_initial_size(
>  	if (mp->m_flags & XFS_MOUNT_DFLT_IOSIZE)
>  		return 0;
>  
> +	/* If the file is small, then use the minimum prealloc */
> +	if (XFS_ISIZE(ip) < mp->m_dalign)
> +		return 0;
> +
...

... and the same fsb->b conversion applies here.

If the file is larger than the minimum write size but smaller than the
stripe unit, we prealloc by the minimum prealloc size (m_writeio_blocks)
until the file grows beyond the stripe unit. That means if the stripe
unit is smaller than m_writeio_blocks or not specified, we'd just start
right into the dynamic prealloc algorithm. Seems reasonable.

Brian

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  reply	other threads:[~2013-06-12 16:06 UTC|newest]

Thread overview: 56+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-06-12 10:22 [PATCH 00/27] xfs: current patch queue for 3.11 Dave Chinner
2013-06-12 10:22 ` [PATCH 01/27] xfs: update mount options documentation Dave Chinner
2013-06-13 13:34   ` Eric Sandeen
2013-06-14  0:40     ` Dave Chinner
2013-06-14  0:53       ` Eric Sandeen
2013-06-12 10:22 ` [PATCH 02/27] xfs: add pluging for bulkstat readahead Dave Chinner
2013-06-12 10:22 ` [PATCH 03/27] xfs: plug directory buffer readahead Dave Chinner
2013-06-12 10:22 ` [PATCH 04/27] xfs: don't use speculative prealloc for small files Dave Chinner
2013-06-12 16:10   ` Brian Foster [this message]
2013-06-13  0:50     ` Dave Chinner
2013-06-12 10:22 ` [PATCH 05/27] xfs: don't do IO when creating an new inode Dave Chinner
2013-06-12 10:22 ` [PATCH 06/27] xfs: xfs_ifree doesn't need to modify the inode buffer Dave Chinner
2013-06-12 10:22 ` [PATCH 07/27] xfs: Introduce ordered log vector support Dave Chinner
2013-06-12 10:22 ` [PATCH 08/27] xfs: Introduce an ordered buffer item Dave Chinner
2013-06-12 10:22 ` [PATCH 09/27] xfs: Inode create log items Dave Chinner
2013-06-12 10:22 ` [PATCH 10/27] xfs: Inode create transaction reservations Dave Chinner
2013-06-12 10:22 ` [PATCH 11/27] xfs: Inode create item recovery Dave Chinner
2013-06-12 10:22 ` [PATCH 12/27] xfs: Use inode create transaction Dave Chinner
2013-06-12 10:22 ` [PATCH 13/27] xfs: remove local fork format handling from xfs_bmapi_write() Dave Chinner
2013-06-12 10:22 ` [PATCH 14/27] xfs: move getdents code into it's own file Dave Chinner
2013-06-12 10:22 ` [PATCH 15/27] xfs: reshuffle dir2 definitions around for userspace Dave Chinner
2013-06-17 16:05   ` Christoph Hellwig
2013-06-18 21:12     ` Dave Chinner
2013-06-18 21:35       ` Dave Chinner
2013-06-12 10:22 ` [PATCH 16/27] xfs: split out attribute listing code into separate file Dave Chinner
2013-06-12 10:22 ` [PATCH 17/27] xfs: split out attribute fork truncation " Dave Chinner
2013-06-12 10:22 ` [PATCH 18/27] xfs: split out xfs inode operations " Dave Chinner
2013-06-12 14:05   ` Christoph Hellwig
2013-06-13  1:14     ` Dave Chinner
2013-06-13  8:00       ` Dave Chinner
2013-06-17 15:56         ` Christoph Hellwig
2013-06-17 18:14           ` Ben Myers
2013-06-18 20:40             ` Dave Chinner
2013-06-18 21:37               ` Ben Myers
2013-06-18 22:02                 ` Dave Chinner
2013-06-12 10:22 ` [PATCH 19/27] xfs: consolidate xfs_vnodeops.c into xfs_inode_ops.c Dave Chinner
2013-06-12 13:59   ` Christoph Hellwig
2013-06-13  1:39     ` Dave Chinner
2013-06-17 16:02       ` Christoph Hellwig
2013-06-18 20:55         ` Dave Chinner
2013-06-12 10:22 ` [PATCH 20/27] xfs: move xfs_getbmap to xfs_extent_ops.c Dave Chinner
2013-06-12 10:22 ` [PATCH 21/27] xfs: introduce xfs_sb.c for sharing with libxfs Dave Chinner
2013-06-12 10:22 ` [PATCH 22/27] xfs: move xfs_trans_reservations to xfs_trans.h Dave Chinner
2013-06-12 10:22 ` [PATCH 23/27] xfs: sync minor header differences needed by userspace Dave Chinner
2013-06-12 10:22 ` [PATCH 24/27] xfs: move xfs_bmap_punch_delalloc() to xfs_aops.c Dave Chinner
2013-06-12 14:06   ` Christoph Hellwig
2013-06-13  1:39     ` Dave Chinner
2013-06-12 10:22 ` [PATCH 25/27] xfs: split out transaction reservation code Dave Chinner
2013-06-12 10:22 ` [PATCH 26/27] xfs: minor cleanups Dave Chinner
2013-06-12 10:22 ` [PATCH 27/27] xfs: fix issues that cause userspace warnings Dave Chinner
2013-06-17 19:32   ` Brian Foster
2013-06-18 21:42     ` Dave Chinner
2013-06-12 13:06 ` [PATCH 00/27] xfs: current patch queue for 3.11 Brian Foster
2013-06-13  1:40   ` Dave Chinner
2013-06-12 14:17 ` Ben Myers
2013-06-13  1:58   ` Dave Chinner

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