On 2/5/18 8:20 AM, Ming Lei wrote:

Hi All,

This patchset supports global tags which was started by Hannes originally:

	https://marc.info/?l=linux-block&m=149132580511346&w=2

Also inroduce 'force_blk_mq' and 'host_tagset' to 'struct scsi_host_template',
so that driver can avoid to support two IO paths(legacy and blk-mq), especially
recent discusion mentioned that SCSI_MQ will be enabled at default soon.

	https://marc.info/?l=linux-scsi&m=151727684915589&w=2

With the above changes, it should be easier to convert SCSI drivers'
reply queue into blk-mq's hctx, then the automatic irq affinity issue can
be solved easily, please see detailed descrption in commit log and the
8th patch for converting HPSA.

Also drivers may require to complete request on the submission CPU
for avoiding hard/soft deadlock, which can be done easily with blk_mq
too.

	https://marc.info/?t=151601851400001&r=1&w=2

The 6th patch uses the introduced 'force_blk_mq' to fix virtio_scsi
so that IO hang issue can be avoided inside legacy IO path, this issue is
a bit generic, at least HPSA/virtio-scsi are found broken with v4.15+.

The 7th & 8th patch fixes HPSA's IO issue which is caused by the reply
queue selection algorithem.

Laurence has verified that this patch makes HPSA working with the linus
tree with this patchset.

Do you have any performance numbers for this patchset? I'd be curious
to know how big the hit is.

-- 
Jens Axboe