On 4/27/18 9:48 AM, Bart Van Assche wrote: > 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. It's a (scalable) hack to count those as well. Going forward they should be converted to just using reserved tags, of course. -- Jens Axboe
