Re: [PATCH][RF C/T/D] Unmapped page cache control - via boot parameter

[Christoph Hellwig]

On Wed, Mar 17, 2010 at 06:22:29PM +0200, Avi Kivity wrote:
> They should be reorderable.  Otherwise host filesystems on several 
> volumes would suffer the same problems.

They are reordable, just not as extremly as the the page cache.
Remember that the request queue really is just a relatively small queue
of outstanding I/O, and that is absolutely intentional.  Large scale
_caching_ is done by the VM in the pagecache, with all the usual aging,
pressure, etc algorithms applied to it.  The block devices have a
relatively small fixed size request queue associated with it to
facilitate request merging and limited reordering and having fully
set up I/O requests for the device.

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/