[Xen-devel] blkif sort queue

Eric Mowat
Thu, 07 Oct 2004 06:02:06 -0000

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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