Re: [PATCH] virtio-blk: make the queue depth the max supportable by the hypervisor

[Theodore Ts'o]

On Sat, Mar 15, 2014 at 06:57:23AM -0700, Christoph Hellwig wrote:
> I don't think this should be a module parameter.  The default sizing
> should be based of the parameters of the actual virtqueue, and if we
> want to allow tuning it it should be by a sysfs attribute, preferable
> using the same semantics as SCSI.

I wanted that too, but looking at the multiqueue code, it wasn't all
obvious how to safely adjust the queue depth once the virtio-blk
device driver is initialized and becomes active.  There are all sorts
data structures including bitmaps, etc. that would have to be resized,
and I decided it would be too difficult / risky for me to make it be
dynamically resizeable.

So I settled on a module parameter thinking it would mostly only used
by testers / benchmarkers.

Can someone suggest a way to do a dynamic resizing of the virtio-blk
queue depth easily / safely?

    	    	      	     	- Ted
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