From: Ming Lei <ming.lei@redhat.com>
To: Jianchao Wang <jianchao.w.wang@oracle.com>
Cc: axboe@kernel.dk, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH V7 1/4] blk-mq: refactor the code of issue request directly
Date: Wed, 14 Nov 2018 17:11:55 +0800 [thread overview]
Message-ID: <20181114091153.GB20550@ming.t460p> (raw)
In-Reply-To: <1542185131-15029-2-git-send-email-jianchao.w.wang@oracle.com>
On Wed, Nov 14, 2018 at 04:45:28PM +0800, Jianchao Wang wrote:
> Merge blk_mq_try_issue_directly and __blk_mq_try_issue_directly
> into one interface to unify the interfaces to issue requests
> directly. The merged interface takes over the requests totally,
> it could insert, end or do nothing based on the return value of
> .queue_rq and 'bypass' parameter. Then caller needn't any other
> handling any more.
>
> Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
> ---
> block/blk-mq.c | 93 ++++++++++++++++++++++++++++------------------------------
> 1 file changed, 45 insertions(+), 48 deletions(-)
>
> diff --git a/block/blk-mq.c b/block/blk-mq.c
> index 411be60..14b4d06 100644
> --- a/block/blk-mq.c
> +++ b/block/blk-mq.c
> @@ -1766,78 +1766,75 @@ static blk_status_t __blk_mq_issue_directly(struct blk_mq_hw_ctx *hctx,
> return ret;
> }
>
> -static blk_status_t __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
> +static blk_status_t blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx,
> struct request *rq,
> blk_qc_t *cookie,
> - bool bypass_insert)
> + bool bypass)
> {
> struct request_queue *q = rq->q;
> bool run_queue = true;
> + blk_status_t ret = BLK_STS_RESOURCE;
> + int srcu_idx;
>
> + hctx_lock(hctx, &srcu_idx);
> /*
> - * RCU or SRCU read lock is needed before checking quiesced flag.
> + * hctx_lock is needed before checking quiesced flag.
> *
> - * When queue is stopped or quiesced, ignore 'bypass_insert' from
> - * blk_mq_request_issue_directly(), and return BLK_STS_OK to caller,
> - * and avoid driver to try to dispatch again.
> + * When queue is stopped or quiesced, ignore 'bypass', insert
> + * and return BLK_STS_OK to caller, and avoid driver to try to
> + * dispatch again.
> */
> - if (blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)) {
> + if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q))) {
> run_queue = false;
> - bypass_insert = false;
> - goto insert;
> + bypass = false;
> + goto out_unlock;
> }
>
> - if (q->elevator && !bypass_insert)
> - goto insert;
> + /*
> + * Bypass the potential scheduler on the bottom device.
> + */
> + if (unlikely(q->elevator && !bypass))
> + goto out_unlock;
>
> - if (!blk_mq_get_dispatch_budget(hctx))
> - goto insert;
> + if (unlikely(!blk_mq_get_dispatch_budget(hctx)))
> + goto out_unlock;
The unlikely annotation is a bit misleading, since out-of-budget can
happen frequently in case of low queue depth, and there are lots of
such examples.
>
> - if (!blk_mq_get_driver_tag(rq)) {
> + if (unlikely(!blk_mq_get_driver_tag(rq))) {
Same with above.
Thanks,
Ming
next prev parent reply other threads:[~2018-11-14 9:12 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-14 8:45 [PATCH V7 0/4] blk-mq: refactor and fix on issue request directly Jianchao Wang
2018-11-14 8:45 ` [PATCH V7 1/4] blk-mq: refactor the code of " Jianchao Wang
2018-11-14 9:11 ` Ming Lei [this message]
2018-11-14 9:23 ` jianchao.wang
2018-11-14 9:43 ` Ming Lei
2018-11-14 15:22 ` Jens Axboe
2018-11-15 1:35 ` jianchao.wang
2018-11-14 8:45 ` [PATCH V7 2/4] blk-mq: fix issue directly case when q is stopped or quiesced Jianchao Wang
2018-11-14 9:20 ` Ming Lei
2018-11-14 9:29 ` jianchao.wang
2018-11-14 9:35 ` Ming Lei
2018-11-15 1:37 ` jianchao.wang
2018-11-14 8:45 ` [PATCH V7 3/4] blk-mq: issue directly with bypass 'false' in blk_mq_sched_insert_requests Jianchao Wang
2018-11-14 8:45 ` [PATCH V7 4/4] blk-mq: replace and kill blk_mq_request_issue_directly Jianchao Wang
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