blkif sort queue

[Eric Mowat <Eric.Mowat@netapp.com>]

Hi, I'm one of the engineers working on the FreeBSD port and while 
upgrading to TOT, I noticed that there appears to only be 1 sort queue 
for all guest domain devices (xlbd_blk_queue).  All disks end up 
pointing at this request queue.  The strategy call (do_blkif_request) 
uses this global queue and attempts to dequeue using elevator sort.  
Does any kind of sort make sense given that multiple devices feed this 
queue?

I ask because some of the new recovery code attempts to call 
kick_pending_request_queues() in blkif_connect().  In my FreeBSD version 
prior to this I was using per disk sort queues, which was fine since I 
would only try to kick the i/o on interrupt completion.  In this newer 
context it seems like having only 1 queue avoids the need to keep a 
table of per-disk sort queues. 

Thanks for any help.

    Eric


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