[PATCH] xfs: increase prealloc size to double that of the previous extent

[Ben Myers]

On Mon, Feb 18, 2013 at 06:57:07PM -0500, Brian Foster wrote:
> The updated speculative preallocation algorithm becomes less
> effective in situations with a high number of concurrent,
> sequential writers. In running 32 sequential writers on a system
> with 32GB RAM, preallocs become fixed at a value of around 128MB.
> Update the heuristic to base the size of the prealloc on double
> the size of the preceding extent. This preserves the original
> aggressive speculative preallocation behavior at a slight cost of
> increasing the size of preallocated data regions following holes of
> sparse files.
> 
> Signed-off-by: Brian Foster <bfoster at redhat.com>

Applied.

-Ben