[dm-devel] dm-crypt performance

[Christoph Hellwig]

On Mon, Mar 25, 2013 at 11:47:22PM -0400, Mikulas Patocka wrote:
> If I sort the requests in dm-crypt to come out in the same order as they 
> were received, there is no longer any slowdown, the new crypt performs as 
> well as the old crypt, but the last time I submitted the patches, people 
> objected to sorting requests in dm-crypt, saying that the I/O scheduler 
> should sort them. But it doesn't. This problem still persists in the 
> current kernels.

FYI, XFS also does it's own request ordering for the metadata buffers,
because it knows the needed ordering and has a bigger view than than
than especially CFQ.  You at least have precedence in a widely used
subsystem for this code.