On Fri, 2018-04-27 at 09:39 -0600, Jens Axboe wrote: > blk_mq_tagset_busy_iter(&shost->tag_set, scsi_host_check_in_flight, > &in_flight); > return in_flight.cnt + atomic_read(&shost->host_busy); > > The atomic read is basically free, once we get rid of the dirty of that > variable on each IO. Hello Jens, What makes you think that " + atomic_read(&shost->host_busy)" is necessary? I am not aware of any code outside the SCSI core that modifies the host_busy member. Thanks, Bart.