> Il giorno 17 gen 2017, alle ore 03:47, Jens Axboe <ax...@fb.com> ha scritto: > > On 12/22/2016 09:49 AM, Paolo Valente wrote: >> >>> Il giorno 17 dic 2016, alle ore 01:12, Jens Axboe <ax...@fb.com> ha scritto: >>> >>> This is basically identical to deadline-iosched, except it registers >>> as a MQ capable scheduler. This is still a single queue design. >>> >> >> One last question (for today ...):in mq-deadline there are no >> "schedule dispatch" or "unplug work" functions. In blk, CFQ and BFQ >> do these schedules/unplugs in a lot of cases. What's the right >> replacement? Just doing nothing? > > You just use blk_mq_run_hw_queue() or variants thereof to kick off queue > runs. >
Hi Jens, I'm working on this right now. I have a pair of quick questions about performance. In the blk version of bfq, if the in-service bfq_queue happen to have no more budget when the bfq dispatch function is invoked, then bfq: returns no request (NULL), immediately expires the in-service bfq_queue, and schedules a new dispatch. The third step is taken so that, if other bfq_queues have requests, then a new in-service bfq_queue will be selected on the upcoming new dispatch, and a new request will be provided right away. My questions are: is this dispatch-schedule step still needed with blk-mq, to avoid a stall? If it is not needed to avoid a stall, would it still be needed to boost throughput, because it would force an immediate, next dispatch? BTW, bfq-mq survived its first request completion. I will provide you with a link to a github branch as soon as bfq-mq seems able to stand up with a minimal workload. Thanks, Paolo > -- > Jens Axboe >
