From: Bart Van Assche <Bart.VanAssche@sandisk.com>
To: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"axboe@fb.com" <axboe@fb.com>
Cc: "osandov@osandov.com" <osandov@osandov.com>
Subject: Re: [PATCH 08/10] blk-mq-sched: add framework for MQ capable IO schedulers
Date: Thu, 12 Jan 2017 21:45:16 +0000 [thread overview]
Message-ID: <1484257502.2720.21.camel@sandisk.com> (raw)
In-Reply-To: <1484170803-9311-9-git-send-email-axboe@fb.com>
On Wed, 2017-01-11 at 14:40 -0700, Jens Axboe wrote:
> @@ -451,11 +456,11 @@ void blk_insert_flush(struct request *rq)
> * processed directly without going through flush machinery. Queue
> * for normal execution.
> */
> - if ((policy & REQ_FSEQ_DATA) &&
> - !(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH))) {
> - if (q->mq_ops) {
> - blk_mq_insert_request(rq, false, true, false);
> - } else
> + if (((policy & REQ_FSEQ_DATA) &&
> + !(policy & (REQ_FSEQ_PREFLUSH | REQ_FSEQ_POSTFLUSH)))) {
> + if (q->mq_ops)
> + blk_mq_sched_insert_request(rq, false, true, false);
> + else
> list_add_tail(&rq->queuelist, &q->queue_head);
> return;
> }
Not that it really matters, but this change adds a pair of parentheses --
"if (e)" is changed into "if ((e))". Is this necessary?
> +void blk_mq_sched_free_hctx_data(struct request_queue *q,
> + void (*exit)(struct blk_mq_hw_ctx *))
> +{
> + struct blk_mq_hw_ctx *hctx;
> + int i;
> +
> + queue_for_each_hw_ctx(q, hctx, i) {
> + if (exit)
> + exit(hctx);
> + kfree(hctx->sched_data);
> + hctx->sched_data = NULL;
> + }
> +}
> +EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
> +
> +int blk_mq_sched_init_hctx_data(struct request_queue *q, size_t size,
> + int (*init)(struct blk_mq_hw_ctx *),
> + void (*exit)(struct blk_mq_hw_ctx *))
> +{
> + struct blk_mq_hw_ctx *hctx;
> + int ret;
> + int i;
> +
> + queue_for_each_hw_ctx(q, hctx, i) {
> + hctx->sched_data = kmalloc_node(size, GFP_KERNEL, hctx->numa_node);
> + if (!hctx->sched_data) {
> + ret = -ENOMEM;
> + goto error;
> + }
> +
> + if (init) {
> + ret = init(hctx);
> + if (ret) {
> + /*
> + * We don't want to give exit() a partially
> + * initialized sched_data. init() must clean up
> + * if it fails.
> + */
> + kfree(hctx->sched_data);
> + hctx->sched_data = NULL;
> + goto error;
> + }
> + }
> + }
> +
> + return 0;
> +error:
> + blk_mq_sched_free_hctx_data(q, exit);
> + return ret;
> +}
If one of the init() calls by blk_mq_sched_init_hctx_data() fails then
blk_mq_sched_free_hctx_data() will call exit() even for hctx's for which
init() has not been called. How about changing "if (exit)" into "if (exit &&
hctx->sched_data)" such that exit() is only called for hctx's for which
init() has been called?
> +struct request *blk_mq_sched_get_request(struct request_queue *q,
> + struct bio *bio,
> + unsigned int op,
> + struct blk_mq_alloc_data *data)
> +{
> + struct elevator_queue *e = q->elevator;
> + struct blk_mq_hw_ctx *hctx;
> + struct blk_mq_ctx *ctx;
> + struct request *rq;
> +
> + blk_queue_enter_live(q);
> + ctx = blk_mq_get_ctx(q);
> + hctx = blk_mq_map_queue(q, ctx->cpu);
> +
> + blk_mq_set_alloc_data(data, q, 0, ctx, hctx);
> +
> + if (e) {
> + data->flags |= BLK_MQ_REQ_INTERNAL;
> + if (e->type->ops.mq.get_request)
> + rq = e->type->ops.mq.get_request(q, op, data);
> + else
> + rq = __blk_mq_alloc_request(data, op);
> + } else {
> + rq = __blk_mq_alloc_request(data, op);
> + if (rq) {
> + rq->tag = rq->internal_tag;
> + rq->internal_tag = -1;
> + }
> + }
> +
> + if (rq) {
> + rq->elv.icq = NULL;
> + if (e && e->type->icq_cache)
> + blk_mq_sched_assign_ioc(q, rq, bio);
> + data->hctx->queued++;
> + return rq;
> + }
> +
> + blk_queue_exit(q);
> + return NULL;
> +}
The "rq->tag = rq->internal_tag; rq->internal_tag = -1;" occurs not only
here but also in blk_mq_alloc_request_hctx(). Has it been considered to move
that code into __blk_mq_alloc_request()?
@@ -223,14 +225,17 @@ struct request *__blk_mq_alloc_request(struct blk_mq_alloc_data *data,
>
> tag = blk_mq_get_tag(data);
> if (tag != BLK_MQ_TAG_FAIL) {
> - rq = data->hctx->tags->rqs[tag];
> + struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
> +
> + rq = tags->rqs[tag];
>
> if (blk_mq_tag_busy(data->hctx)) {
> rq->rq_flags = RQF_MQ_INFLIGHT;
> atomic_inc(&data->hctx->nr_active);
> }
>
> - rq->tag = tag;
> + rq->tag = -1;
> + rq->internal_tag = tag;
> blk_mq_rq_ctx_init(data->q, data->ctx, rq, op);
> return rq;
> }
How about using the following code for tag assignment instead of "rq->tag =
-1; rq->internal_tag = tag"?
if (data->flags & BLK_MQ_REQ_INTERNAL) {
rq->tag = -1;
rq->internal_tag = tag;
} else {
rq->tag = tag;
rq->internal_tag = -1;
}
> @@ -313,6 +313,9 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q, int rw,
> goto out_queue_exit;
> }
>
> + rq->tag = rq->internal_tag;
> + rq->internal_tag = -1;
> +
> return rq;
>
> out_queue_exit:
> @@ -321,10 +324,10 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q, int rw,
> }
> EXPORT_SYMBOL_GPL(blk_mq_alloc_request_hctx);
Should something like "WARN_ON_ONCE(flags & BLK_MQ_REQ_INTERNAL)" be added
at the start of this function to avoid that BLK_MQ_REQ_INTERNAL is passed in
from outside the block layer?
Bart.
next prev parent reply other threads:[~2017-01-12 21:45 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-01-11 21:39 [PATCHSET v6] blk-mq scheduling framework Jens Axboe
2017-01-11 21:39 ` [PATCH 01/10] block: move existing elevator ops to union Jens Axboe
2017-01-12 10:15 ` Johannes Thumshirn
2017-01-12 21:17 ` Bart Van Assche
2017-01-13 8:34 ` Christoph Hellwig
2017-01-13 15:00 ` Jens Axboe
2017-01-11 21:39 ` [PATCH 02/10] blk-mq: make mq_ops a const pointer Jens Axboe
2017-01-12 10:14 ` Johannes Thumshirn
2017-01-13 8:16 ` Christoph Hellwig
2017-01-11 21:39 ` [PATCH 03/10] block: move rq_ioc() to blk.h Jens Axboe
2017-01-12 10:14 ` Johannes Thumshirn
2017-01-12 21:18 ` Bart Van Assche
2017-01-13 8:33 ` Christoph Hellwig
2017-01-11 21:39 ` [PATCH 04/10] blk-mq: un-export blk_mq_free_hctx_request() Jens Axboe
2017-01-12 10:13 ` Johannes Thumshirn
2017-01-12 21:18 ` Bart Van Assche
2017-01-13 8:16 ` Christoph Hellwig
2017-01-11 21:39 ` [PATCH 05/10] blk-mq: export some helpers we need to the scheduling framework Jens Axboe
2017-01-12 10:17 ` Johannes Thumshirn
2017-01-12 21:20 ` Bart Van Assche
2017-01-13 8:17 ` Christoph Hellwig
2017-01-13 15:01 ` Jens Axboe
2017-01-11 21:39 ` [PATCH 06/10] blk-mq-tag: cleanup the normal/reserved tag allocation Jens Axboe
2017-01-12 21:22 ` Bart Van Assche
2017-01-12 22:07 ` Jens Axboe
2017-01-13 8:30 ` Christoph Hellwig
2017-01-13 15:06 ` Jens Axboe
2017-01-11 21:40 ` [PATCH 07/10] blk-mq: abstract out helpers for allocating/freeing tag maps Jens Axboe
2017-01-12 21:29 ` Bart Van Assche
2017-01-12 21:54 ` Jens Axboe
2017-01-13 8:25 ` Johannes Thumshirn
2017-01-11 21:40 ` [PATCH 08/10] blk-mq-sched: add framework for MQ capable IO schedulers Jens Axboe
2017-01-12 21:45 ` Bart Van Assche [this message]
2017-01-12 21:59 ` Jens Axboe
2017-01-13 11:15 ` Hannes Reinecke
2017-01-13 16:39 ` Bart Van Assche
2017-01-13 16:41 ` Omar Sandoval
2017-01-13 17:43 ` Hannes Reinecke
2017-01-11 21:40 ` [PATCH 09/10] mq-deadline: add blk-mq adaptation of the deadline IO scheduler Jens Axboe
2017-01-12 21:53 ` Bart Van Assche
2017-01-11 21:40 ` [PATCH 10/10] blk-mq-sched: allow setting of default " Jens Axboe
2017-01-12 21:54 ` Bart Van Assche
2017-01-12 21:16 ` [PATCHSET v6] blk-mq scheduling framework Bart Van Assche
2017-01-13 8:15 ` Hannes Reinecke
2017-01-13 11:04 ` Hannes Reinecke
2017-01-13 12:10 ` Hannes Reinecke
2017-01-13 15:05 ` Jens Axboe
2017-01-13 15:03 ` Jens Axboe
2017-01-13 15:23 ` Jens Axboe
2017-01-13 15:33 ` Hannes Reinecke
2017-01-13 15:34 ` Jens Axboe
2017-01-13 15:59 ` Hannes Reinecke
2017-01-13 16:00 ` Jens Axboe
2017-01-13 16:02 ` Jens Axboe
2017-01-13 21:45 ` Jens Axboe
2017-01-16 8:11 ` Hannes Reinecke
2017-01-16 15:12 ` Jens Axboe
2017-01-16 15:16 ` Jens Axboe
2017-01-16 15:47 ` Jens Axboe
2017-01-13 10:09 ` Hannes Reinecke
2017-01-15 10:12 ` Paolo Valente
2017-01-15 15:55 ` Jens Axboe
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