On Thu, Jan 23, 2020 at 11:29 AM Jens Axboe <axboe@xxxxxxxxx> wrote: > > > Please don't top post, we just lost all context here unless I had fixed > it up for you. > > > On 1/23/20 12:25 PM, Muraliraja Muniraju wrote: > > > > On Thu, Jan 23, 2020 at 10:59 AM Jens Axboe <axboe@xxxxxxxxx> wrote: > >> > >> On 1/21/20 12:25 PM, muraliraja.muniraju wrote: > >>> Current loop device implementation has a single kthread worker and > >>> drains one request at a time to completion. If the underneath device is > >>> slow then this reduces the concurrency significantly. To help in these > >>> cases, adding multiple loop workers increases the concurrency. Also to > >>> retain the old behaviour the default number of loop workers is 1 and can > >>> be tuned via the ioctl. > >> > >> Have you considered using blk-mq for this? Right now loop just does > >> some basic checks and then queues for a thread. If you bump nr_hw_queues > >> up (provide a parameter for that) and set BLK_MQ_F_BLOCKING in the > >> tag flags, then that might be a more viable approach for handling this. > > > > I see that the kernel is already is using the multi queues with the > > number of hardware queues is 1. But the problem IMO is that the worker > > seems to be processing 1 request at a time, to parallelize requests > > and have more concurrency more workers needs to be added. I also tried > > increasing the nr_hw_queues without increasing the number of workers, > > I did not see any difference in performance and it stayed the same. It > > allows to queue more requests but it is processed one at a time. I > > have not tried with enabling BLK_MQ_F_BLOCKING though. I see that it > > can schedule requests early. > > The experiment is useless without BLK_MQ_F_BLOCKING set, so you need > that at least. With that, you _will_ see work items processed in > parallel, depending on where they are queued from. > > -- > Jens Axboe > Sure, let me try setting the BLK_MQ_F_BLOCKING on the existing patch that I sent and see. Will update soon, Thanks.
