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From: Kashyap Desai <kashyap.desai@broadcom.com>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
	linux-block@vger.kernel.org, linux-scsi@vger.kernel.org,
	"Martin K . Petersen" <martin.petersen@oracle.com>,
	James Bottomley <James.Bottomley@hansenpartnership.com>,
	Bart Van Assche <bvanassche@acm.org>,
	Hannes Reinecke <hare@suse.com>,
	John Garry <john.garry@huawei.com>,
	Don Brace <don.brace@microsemi.com>,
	Sathya Prakash Veerichetty <sathya.prakash@broadcom.com>,
	Christoph Hellwig <hch@lst.de>
Subject: RE: [PATCH 8/9] scsi: megaraid: convert private reply queue to blk-mq hw queue
Date: Sun, 2 Jun 2019 22:04:01 +0530
Message-ID: <020a7707a31803d65dd94cc0928a425a@mail.gmail.com> (raw)
In-Reply-To: <20190602074757.GA31572@ming.t460p>

> Meantime please try the following patch and see if difference can be
made.
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c index
> 49d73d979cb3..d2abec3b0f60 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -589,7 +589,7 @@ static void __blk_mq_complete_request(struct
> request *rq)
>  	 * So complete IO reqeust in softirq context in case of single
queue
>  	 * for not degrading IO performance by irqsoff latency.
>  	 */
> -	if (q->nr_hw_queues == 1) {
> +	if (q->nr_hw_queues == 1 || (rq->mq_hctx->flags &
> BLK_MQ_F_HOST_TAGS))
> +{
>  		__blk_complete_request(rq);
>  		return;
>  	}
> @@ -1977,7 +1977,8 @@ static blk_qc_t blk_mq_make_request(struct
> request_queue *q, struct bio *bio)
>  		/* bypass scheduler for flush rq */
>  		blk_insert_flush(rq);
>  		blk_mq_run_hw_queue(data.hctx, true);
> -	} else if (plug && (q->nr_hw_queues == 1 || q->mq_ops-
> >commit_rqs)) {
> +	} else if (plug && (q->nr_hw_queues == 1 || q->mq_ops->commit_rqs
> ||
> +				(data.hctx->flags & BLK_MQ_F_HOST_TAGS)))
> {
>  		/*
>  		 * Use plugging if we have a ->commit_rqs() hook as well,
as
>  		 * we know the driver uses bd->last in a smart fashion.

Ming -

I tried above patch and no improvement in performance.

Below is perf record data - lock contention is while getting the tag
(blk_mq_get_tag )

6.67%     6.67%  fio              [kernel.vmlinux]  [k]
native_queued_spin_lock_slowpath
   - 6.66% io_submit
      - 6.66% entry_SYSCALL_64
         - do_syscall_64
            - 6.66% __x64_sys_io_submit
               - 6.66% io_submit_one
                  - 6.66% aio_read
                     - 6.66% generic_file_read_iter
                        - 6.66% blkdev_direct_IO
                           - 6.65% submit_bio
                              - generic_make_request
                                 - 6.65% blk_mq_make_request
                                    - 6.65% blk_mq_get_request
                                       - 6.65% blk_mq_get_tag
                                          - 6.58%
prepare_to_wait_exclusive
                                             - 6.57%
_raw_spin_lock_irqsave

queued_spin_lock_slowpath

>
> thanks,
> Ming

  reply index

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-31  2:27 [PATCH 0/9] blk-mq/scsi: convert private reply queue into blk_mq " Ming Lei
2019-05-31  2:27 ` [PATCH 1/9] blk-mq: allow hw queues to share hostwide tags Ming Lei
2019-05-31  6:07   ` Hannes Reinecke
2019-05-31 15:37   ` Bart Van Assche
2019-06-24  8:44     ` Ming Lei
2019-06-05 14:10   ` John Garry
2019-06-24  8:46     ` Ming Lei
2019-06-24 13:14       ` John Garry
2019-05-31  2:27 ` [PATCH 2/9] block: null_blk: introduce module parameter of 'g_host_tags' Ming Lei
2019-05-31  6:08   ` Hannes Reinecke
2019-05-31 15:39   ` Bart Van Assche
2019-06-24  8:43     ` Ming Lei
2019-06-02  1:56   ` Minwoo Im
2019-05-31  2:27 ` [PATCH 3/9] scsi: Add template flag 'host_tagset' Ming Lei
2019-05-31  6:08   ` Hannes Reinecke
2019-05-31  2:27 ` [PATCH 4/9] scsi_debug: support host tagset Ming Lei
2019-05-31  6:09   ` Hannes Reinecke
2019-06-02  2:03   ` Minwoo Im
2019-06-02 17:01   ` Douglas Gilbert
2019-05-31  2:27 ` [PATCH 5/9] scsi: introduce scsi_cmnd_hctx_index() Ming Lei
2019-05-31  6:10   ` Hannes Reinecke
2019-05-31  2:27 ` [PATCH 6/9] scsi: hpsa: convert private reply queue to blk-mq hw queue Ming Lei
2019-05-31  6:15   ` Hannes Reinecke
2019-05-31  6:30     ` Ming Lei
2019-05-31  6:40       ` Hannes Reinecke
2019-05-31  2:27 ` [PATCH 7/9] scsi: hisi_sas_v3: " Ming Lei
2019-05-31  6:20   ` Hannes Reinecke
2019-05-31  6:34     ` Ming Lei
2019-05-31  6:42       ` Hannes Reinecke
2019-05-31  7:14         ` Ming Lei
2019-05-31 11:38       ` John Garry
2019-06-03 11:00         ` Ming Lei
2019-06-03 13:00           ` John Garry
2019-06-04 13:37             ` Ming Lei
2019-05-31  2:28 ` [PATCH 8/9] scsi: megaraid: " Ming Lei
2019-05-31  6:22   ` Hannes Reinecke
2019-06-01 21:41   ` Kashyap Desai
2019-06-02  6:42     ` Ming Lei
2019-06-02  7:48       ` Ming Lei
2019-06-02 16:34         ` Kashyap Desai [this message]
2019-06-03  3:56           ` Ming Lei
2019-06-03 10:00             ` Kashyap Desai
2019-06-07  9:45             ` Kashyap Desai
2019-05-31  2:28 ` [PATCH 9/9] scsi: mp3sas: " Ming Lei
2019-05-31  6:23   ` Hannes Reinecke
2019-06-06 11:58   ` Sreekanth Reddy
2019-06-04  8:49 ` [PATCH 0/9] blk-mq/scsi: convert private reply queue into blk_mq " John Garry
2019-08-13  8:30   ` John Garry

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