Re: [PATCH] scsi: storvsc: Cap scsi_driver.can_queue to fix a hang issue during boot

[John Garry]

On 06/10/2021 17:08, Michael Kelley wrote:
> > > The calculated value of can_queue is not realistic.  The blk-mq layer
> > > caps the number of tags at 10240,
> > nit: 1024, I think
> I was thinking about BLK_MQ_MAX_DEPTH (#define'd as 10240), which
> is used to limit the tag set size in blk_mq_alloc_tag_set().   When running
> on large VMs on Hyper-V, we can see the "blk-mq: reduced tag depth
> to 10240" message.:-(

Ah, right. The other related capping is the sdev queue depth, which is 
now capped at max(1024, can_queue), see scsi_device_max_queue_depth().

Thanks,
John