Re: [dm-devel] [PATCH] dm-kcopyd/dm-snap: Don't read the origin on full chunk write

[Joe Thornber <thornber redhat com>]

On Fri, Jun 17, 2011 at 08:32:36AM -0400, Mikulas Patocka wrote:
> Hi
> 
> This optimizes full chunk writes for snapshots.
> 
> Note that there is a performance bug in device mapper that it doesn't ever 
> send bios larger than 4k to snapshots. So this patch optimizes only 4k 
> chunk sizes. Once the 4k limit will be removed from device mapper, this 
> patch could optimize any chunk size.

Nack.  If you don't need to copy, don't send it to kcopyd.

- Joe