Hello Tejun,

Tejun Heo, on 08/12/2010 04:41 PM wrote:

Nobody is making meaningful use of ORDERED_BY_TAG now and queue
draining for barrier requests will be removed soon which will render
the advantage of tag ordering moot.

Have you seen Hannes Reinecke's and my measurements in 
http://marc.info/?l=linux-scsi&m=128110662528485&w=2 and 
http://marc.info/?l=linux-scsi&m=128111995217405&w=2 correspondingly?

If yes, what else evidences do you need to see that the tag ordering is 
a big performance win?

Vlad