tree 6658e13f80d4f6450f5a69c82d3bf1b590ecf234
parent 1f98a13f623e0ef666690a18c1250335fc6d7ef1
author Jens Axboe <jens.axboe@oracle.com> 1248934704 +0200
committer Jens Axboe <jens.axboe@oracle.com> 1252672411 +0200

block: improve queue_should_plug() by looking at IO depths

Instead of just checking whether this device uses block layer
tagging, we can improve the detection by looking at the maximum
queue depth it has reached. If that crosses 4, then deem it a
queuing device.

This is important on high IOPS devices, since plugging hurts
the performance there (it can be as much as 10-15% of the sys
time).

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>