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* [PATCH V6 0/6] blk-mq: support batching dispatch from scheduler
@ 2020-06-24 23:03 Ming Lei
  2020-06-24 23:03 ` [PATCH V6 1/6] blk-mq: pass request queue into get/put budget callback Ming Lei
                   ` (5 more replies)
  0 siblings, 6 replies; 14+ messages in thread
From: Ming Lei @ 2020-06-24 23:03 UTC (permalink / raw)
  To: Jens Axboe
  Cc: linux-block, Ming Lei, Sagi Grimberg, Baolin Wang, Christoph Hellwig

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 previous versions and found performance on MMC can be improved.

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@grimberg.me/

V6:
	- rebase on for-5.9/block, only 1st patch is changed

V5:
	- code style changes suggested by Damien

V4:
	- fix releasing budgets and avoids IO hang(5/6)
	- dispatch more batches if the device can accept more(6/6)
	- verified by running more tests

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    | 116 +++++++++++++++++++++++++++++++++++-----
 block/blk-mq.c          | 110 +++++++++++++++++++++++--------------
 block/blk-mq.h          |  15 +++---
 drivers/scsi/scsi_lib.c |   8 ++-
 include/linux/blk-mq.h  |   4 +-
 5 files changed, 182 insertions(+), 71 deletions(-)

Cc: Sagi Grimberg <sagi@grimberg.me>
Cc: Baolin Wang <baolin.wang7@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
-- 
2.25.2


^ permalink raw reply	[flat|nested] 14+ messages in thread

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Thread overview: 14+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-06-24 23:03 [PATCH V6 0/6] blk-mq: support batching dispatch from scheduler Ming Lei
2020-06-24 23:03 ` [PATCH V6 1/6] blk-mq: pass request queue into get/put budget callback Ming Lei
2020-06-24 23:03 ` [PATCH V6 2/6] blk-mq: pass hctx to blk_mq_dispatch_rq_list Ming Lei
2020-06-24 23:03 ` [PATCH V6 3/6] blk-mq: move getting driver tag and budget into one helper Ming Lei
2020-06-24 23:03 ` [PATCH V6 4/6] blk-mq: remove dead check from blk_mq_dispatch_rq_list Ming Lei
2020-06-25  7:42   ` Johannes Thumshirn
2020-06-24 23:03 ` [PATCH V6 5/6] blk-mq: pass obtained budget count to blk_mq_dispatch_rq_list Ming Lei
2020-06-29  8:11   ` Christoph Hellwig
2020-06-24 23:03 ` [PATCH V6 6/6] blk-mq: support batching dispatch in case of io scheduler Ming Lei
2020-06-29  9:04   ` Christoph Hellwig
2020-06-29 10:32     ` Ming Lei
2020-06-30  0:57       ` Ming Lei
2020-06-30  4:56         ` Christoph Hellwig
2020-06-30  4:55       ` Christoph Hellwig

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