On Thu, May 28, 2020 at 4:01 PM Ming Lei <ming.lei@xxxxxxxxxx> wrote: > > Hi Jens, > > More and more drivers want to get batching requests queued from > block layer, such as mmc[1], and tcp based storage drivers[2]. Also > current in-tree users have virtio-scsi, virtio-blk and nvme. > > For none, we already support batching dispatch. > > But for io scheduler, every time we just take one request from scheduler > and pass the single request to blk_mq_dispatch_rq_list(). This way makes > batching dispatch not possible when io scheduler is applied. One reason > is that we don't want to hurt sequential IO performance, becasue IO > merge chance is reduced if more requests are dequeued from scheduler > queue. > > Tries to start the support by dequeuing more requests from scheduler > if budget is enough and device isn't busy. > > Simple fio test over virtio-scsi shows IO can get improved by 5~10%. > > Baolin has tested V1 and found performance on MMC can be improved. > > Patches can be found from the following tree too: > > https://github.com/ming1/linux/commits/v5.7-rc-blk-mq-batching-submission > > Patch 1 ~ 4 are improvement and cleanup, which can't applied without > supporting batching dispatch. > > Patch 5 ~ 6 starts to support batching dispatch from scheduler. > > > [1] https://lore.kernel.org/linux-block/20200512075501.GF1531898@T590/#r > [2] https://lore.kernel.org/linux-block/fe6bd8b9-6ed9-b225-f80c-314746133722@xxxxxxxxxxx/ > > V3: > - add reviewed-by tag > - fix one typo > - fix one budget leak issue in case that .queue_rq returned *_RESOURCE in 5/6 > > V2: > - remove 'got_budget' from blk_mq_dispatch_rq_list > - drop patch for getting driver tag & handling partial dispatch > > Ming Lei (6): > blk-mq: pass request queue into get/put budget callback > blk-mq: pass hctx to blk_mq_dispatch_rq_list > blk-mq: move getting driver tag and budget into one helper > blk-mq: remove dead check from blk_mq_dispatch_rq_list > blk-mq: pass obtained budget count to blk_mq_dispatch_rq_list > blk-mq: support batching dispatch in case of io scheduler > > block/blk-mq-sched.c | 95 ++++++++++++++++++++++++++++----- > block/blk-mq.c | 115 ++++++++++++++++++++++++++-------------- > block/blk-mq.h | 15 +++--- > drivers/scsi/scsi_lib.c | 8 ++- > include/linux/blk-mq.h | 4 +- > 5 files changed, 168 insertions(+), 69 deletions(-) > > Cc: Sagi Grimberg <sagi@xxxxxxxxxxx> > Cc: Baolin Wang <baolin.wang7@xxxxxxxxx> > Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> Works well for me again. So for the whole patch set: Tested-by: Baolin Wang <baolin.wang7@xxxxxxxxx> -- Baolin Wang
