On Mon, Mar 21, 2022 at 12:32:08PM +0530, Kanchan Joshi wrote: > On Mon, Mar 14, 2022 at 10:40:53PM +0800, Ming Lei wrote: > > On Thu, Mar 10, 2022 at 06:10:08PM +0530, Kanchan Joshi wrote: > > > On Thu, Mar 10, 2022 at 2:04 PM Christoph Hellwig <hch@xxxxxx> wrote: > > > > > > > > On Tue, Mar 08, 2022 at 08:50:58PM +0530, Kanchan Joshi wrote: > > > > > From: Jens Axboe <axboe@xxxxxxxxx> > > > > > > > > > > Add support to use plugging if it is enabled, else use default path. > > > > > > > > The subject and this comment don't really explain what is done, and > > > > also don't mention at all why it is done. > > > > > > Missed out, will fix up. But plugging gave a very good hike to IOPS. > > > > But how does plugging improve IOPS here for passthrough request? Not > > see plug->nr_ios is wired to data.nr_tags in blk_mq_alloc_request(), > > which is called by nvme_submit_user_cmd(). > > Yes, one tag at a time for each request, but none of the request gets > dispatched and instead added to the plug. And when io_uring ends the > plug, the whole batch gets dispatched via ->queue_rqs (otherwise it used > to be via ->queue_rq, one request at a time). > > Only .plug impact looks like this on passthru-randread: > > KIOPS(depth_batch) 1_1 8_2 64_16 128_32 > Without plug 159 496 784 785 > With plug 159 525 991 1044 > > Hope it does clarify. OK, thanks for your confirmation, then the improvement should be from batch submission only. If cached request is enabled, I guess the number could be better. Thanks, Ming
