Re: buffered writeback torture program

[Andreas Dilger <adilger@xxxxxxxxx>]

On 2011-04-21, at 11:41 AM, Christoph Hellwig wrote:
> On Thu, Apr 21, 2011 at 01:34:44PM -0400, Chris Mason wrote:
>> Sorry, this doesn't do it.  I think that given what a strange special
>> case this is, we're best off waiting for the IO-less throttling, and
>> maybe changing the code in xfs/ext4 to be a little more seek aware.  Or
>> maybe not, it has to get written eventually either way.
> 
> I'm not sure what you mean with seek aware.  XFS only clusters
> additional pages that are in the same extent, and in fact only does
> so for asynchrononous writeback.  Not sure how this should be more
> seek aware.

But doesn't XFS have potentially very large extents, especially in the case of 
files that were fallocate()'d or linearly written?  If there is a single 8GB 
extent, and then random writes within that extent (seems very database like) 
grouping the all of the writes in the extent doesn't seem so great.


Cheers, Andreas