From: Kashyap Desai <kashyap.desai@broadcom.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: John Garry <john.garry@huawei.com>,
axboe@kernel.dk, jejb@linux.ibm.com, martin.petersen@oracle.com,
don.brace@microsemi.com, Sumit Saxena <sumit.saxena@broadcom.com>,
bvanassche@acm.org, hare@suse.com, hch@lst.de,
Shivasharan Srikanteshwara
<shivasharan.srikanteshwara@broadcom.com>,
linux-block@vger.kernel.org, linux-scsi@vger.kernel.org,
esc.storagedev@microsemi.com, chenxiang66@hisilicon.com,
"PDL,MEGARAIDLINUX" <megaraidlinux.pdl@broadcom.com>
Subject: RE: [PATCH RFC v7 10/12] megaraid_sas: switch fusion adapters to MQ
Date: Thu, 6 Aug 2020 20:07:38 +0530 [thread overview]
Message-ID: <f1ac35dfca34193e6c9bcedbc11911d2@mail.gmail.com> (raw)
In-Reply-To: <20200806133819.GA2046861@T590>
> > Hi Ming -
> >
> > There is still some race which is not handled. Take a case of IO is
> > not able to get budget and it has already marked <restarts> flag.
> > <restarts> flag will be seen non-zero in completion path and
> > completion path will attempt h/w queue run. (But this particular IO is
> > still not in s/w queue.).
> > Attempt of running h/w queue from completion path will not flush any
> > IO since there is no IO in s/w queue.
>
> Then where is the IO to be submitted in case of running out of budget?
Typical race in your latest patch is - (Lets consider command A,B and C)
Command A did not receive budget. Command B completed (which was already
submitted earlier) at the same time and it make sdev->device_busy = 0 from
" scsi_finish_command".
Command B has still not called "scsi_end_request". Command C get the
budget and it will make sdev->device_busy = 1. Now, Command A set set
sdev->restarts flags but will not run h/w queue since sdev->device_busy =
1.
Command B run h/w queue (make sdev->restart = 0) from completion path, but
command -A is still not in the s/w queue. Command-A is in now in s/w
queue. Command-C completed but it will not run h/w queue because
sdev->restarts = 0.
>
> Any IO request which is going to be added to hctx->dispatch, the queue
will be
> re-run via blk-mq core.
>
> Any IO request being issued directly when running out of budget will be
insert
> to hctx->dispatch or sw/scheduler queue, will be run in the submission
path.
I have *not* included below changes we discussed in my testing - If I
include below patch, it is correct that queue will be run in submission
path (at least the path which is impacted in my testing). You have already
mentioned that most of the submission path has fix now in latest kernel
w.r.t running h/w queue from submission path. Below path is missing for
running h/w queue from submission path.
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index
54f9015..bcfd33a 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -173,8 +173,10 @@ static int blk_mq_do_dispatch_ctx(struct
blk_mq_hw_ctx *hctx)
if (!sbitmap_any_bit_set(&hctx->ctx_map))
break;
- if (!blk_mq_get_dispatch_budget(hctx))
+ if (!blk_mq_get_dispatch_budget(hctx)) {
+ blk_mq_delay_run_hw_queue(hctx,
+ BLK_MQ_BUDGET_DELAY);
break;
+ }
rq = blk_mq_dequeue_from_ctx(hctx, ctx);
if (!rq) {
Are you saying above fix should be included along with your latest patch ?
>
>
> Thanks,
> Ming
next prev parent reply other threads:[~2020-08-06 17:28 UTC|newest]
Thread overview: 123+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-10 17:29 [PATCH RFC v7 00/12] blk-mq/scsi: Provide hostwide shared tags for SCSI HBAs John Garry
2020-06-10 17:29 ` [PATCH RFC v7 01/12] blk-mq: rename BLK_MQ_F_TAG_SHARED as BLK_MQ_F_TAG_QUEUE_SHARED John Garry
2020-06-10 17:29 ` [PATCH RFC v7 02/12] blk-mq: rename blk_mq_update_tag_set_depth() John Garry
2020-06-11 2:57 ` Ming Lei
2020-06-11 8:26 ` John Garry
2020-06-23 11:25 ` John Garry
2020-06-23 14:23 ` Hannes Reinecke
2020-06-24 8:13 ` Kashyap Desai
2020-06-29 16:18 ` John Garry
2020-08-10 16:51 ` Kashyap Desai
2020-08-11 8:01 ` John Garry
2020-08-11 16:34 ` Kashyap Desai
2020-06-10 17:29 ` [PATCH RFC v7 03/12] blk-mq: Use pointers for blk_mq_tags bitmap tags John Garry
2020-06-10 17:29 ` [PATCH RFC v7 04/12] blk-mq: Facilitate a shared sbitmap per tagset John Garry
2020-06-11 3:37 ` Ming Lei
2020-06-11 10:09 ` John Garry
2020-06-10 17:29 ` [PATCH RFC v7 05/12] blk-mq: Record nr_active_requests per queue for when using shared sbitmap John Garry
2020-06-11 4:04 ` Ming Lei
2020-06-11 10:22 ` John Garry
2020-06-10 17:29 ` [PATCH RFC v7 06/12] blk-mq: Record active_queues_shared_sbitmap per tag_set " John Garry
2020-06-11 13:16 ` Hannes Reinecke
2020-06-11 14:22 ` John Garry
2020-06-10 17:29 ` [PATCH RFC v7 07/12] blk-mq: Add support in hctx_tags_bitmap_show() for a " John Garry
2020-06-11 13:19 ` Hannes Reinecke
2020-06-11 14:33 ` John Garry
2020-06-12 6:06 ` Hannes Reinecke
2020-06-29 15:32 ` About sbitmap_bitmap_show() and cleared bits (was Re: [PATCH RFC v7 07/12] blk-mq: Add support in hctx_tags_bitmap_show() for a shared sbitmap) John Garry
2020-06-30 6:33 ` Hannes Reinecke
2020-06-30 7:30 ` John Garry
2020-06-30 11:36 ` John Garry
2020-06-30 14:55 ` Bart Van Assche
2020-07-13 9:41 ` [PATCH RFC v7 07/12] blk-mq: Add support in hctx_tags_bitmap_show() for a shared sbitmap John Garry
2020-07-13 12:20 ` Hannes Reinecke
2020-06-10 17:29 ` [PATCH RFC v7 08/12] scsi: Add template flag 'host_tagset' John Garry
2020-06-10 17:29 ` [PATCH RFC v7 09/12] scsi: hisi_sas: Switch v3 hw to MQ John Garry
2020-06-10 17:29 ` [PATCH RFC v7 10/12] megaraid_sas: switch fusion adapters " John Garry
2020-07-02 10:23 ` Kashyap Desai
2020-07-06 8:23 ` John Garry
2020-07-06 8:45 ` Hannes Reinecke
2020-07-06 9:26 ` John Garry
2020-07-06 9:40 ` Hannes Reinecke
2020-07-06 19:19 ` Kashyap Desai
2020-07-07 7:58 ` John Garry
2020-07-07 14:45 ` Kashyap Desai
2020-07-07 16:17 ` John Garry
2020-07-09 19:01 ` Kashyap Desai
2020-07-10 8:10 ` John Garry
2020-07-13 7:55 ` Kashyap Desai
2020-07-13 8:42 ` John Garry
2020-07-19 19:07 ` Kashyap Desai
2020-07-20 7:23 ` Kashyap Desai
2020-07-20 9:18 ` John Garry
2020-07-21 1:13 ` Ming Lei
2020-07-21 6:53 ` Kashyap Desai
2020-07-22 4:12 ` Ming Lei
2020-07-22 5:30 ` Kashyap Desai
2020-07-22 8:04 ` Ming Lei
2020-07-22 9:32 ` John Garry
2020-07-23 14:07 ` Ming Lei
2020-07-23 17:29 ` John Garry
2020-07-24 2:47 ` Ming Lei
2020-07-28 7:54 ` John Garry
2020-07-28 8:45 ` Ming Lei
2020-07-29 5:25 ` Kashyap Desai
2020-07-29 15:36 ` Ming Lei
2020-07-29 18:31 ` Kashyap Desai
2020-08-04 8:36 ` Ming Lei
2020-08-04 9:27 ` Kashyap Desai
2020-08-05 8:40 ` Ming Lei
2020-08-06 10:25 ` Kashyap Desai
2020-08-06 13:38 ` Ming Lei
2020-08-06 14:37 ` Kashyap Desai [this message]
2020-08-06 15:29 ` Ming Lei
2020-08-08 19:05 ` Kashyap Desai
2020-08-09 2:16 ` Ming Lei
2020-08-10 16:38 ` Kashyap Desai
2020-08-11 8:09 ` John Garry
2020-08-04 17:00 ` John Garry
2020-08-05 2:56 ` Ming Lei
2020-07-28 8:01 ` Kashyap Desai
2020-07-08 11:31 ` John Garry
2020-06-10 17:29 ` [PATCH RFC v7 11/12] smartpqi: enable host tagset John Garry
2020-07-14 13:16 ` John Garry
2020-07-14 13:31 ` John Garry
2020-07-14 18:16 ` Don.Brace
2020-07-15 7:28 ` John Garry
2020-07-14 14:02 ` Hannes Reinecke
2020-08-18 8:33 ` John Garry
2020-06-10 17:29 ` [PATCH RFC v7 12/12] hpsa: enable host_tagset and switch to MQ John Garry
2020-07-14 7:37 ` John Garry
2020-07-14 7:41 ` Hannes Reinecke
2020-07-14 7:52 ` John Garry
2020-07-14 8:06 ` Ming Lei
2020-07-14 9:53 ` John Garry
2020-07-14 10:14 ` Ming Lei
2020-07-14 10:43 ` Hannes Reinecke
2020-07-14 10:19 ` Hannes Reinecke
2020-07-14 10:35 ` John Garry
2020-07-14 10:44 ` Ming Lei
2020-07-14 10:52 ` John Garry
2020-07-14 12:04 ` Ming Lei
2020-08-03 20:39 ` Don.Brace
2020-08-04 9:27 ` John Garry
2020-08-04 15:18 ` Don.Brace
2020-08-05 11:21 ` John Garry
2020-08-14 21:04 ` Don.Brace
2020-08-17 8:00 ` John Garry
2020-08-17 18:39 ` Don.Brace
2020-08-18 7:14 ` Hannes Reinecke
2020-07-16 16:14 ` Don.Brace
2020-07-16 19:45 ` Don.Brace
2020-07-17 10:11 ` John Garry
2020-06-11 3:07 ` [PATCH RFC v7 00/12] blk-mq/scsi: Provide hostwide shared tags for SCSI HBAs Ming Lei
2020-06-11 9:35 ` John Garry
2020-06-12 18:47 ` Kashyap Desai
2020-06-15 2:13 ` Ming Lei
2020-06-15 6:57 ` Kashyap Desai
2020-06-16 1:00 ` Ming Lei
2020-06-17 11:26 ` Kashyap Desai
2020-06-22 6:24 ` Hannes Reinecke
2020-06-23 0:55 ` Ming Lei
2020-06-23 11:50 ` Kashyap Desai
2020-06-23 12:11 ` Kashyap Desai
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