From: Paolo Valente <paolo.valente@linaro.org>
To: Jens Axboe <axboe@fb.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org,
Linux-Kernal <linux-kernel@vger.kernel.org>,
osandov@fb.com
Subject: Re: [PATCH 7/8] mq-deadline: add blk-mq adaptation of the deadline IO scheduler
Date: Thu, 16 Feb 2017 11:46:38 +0100 [thread overview]
Message-ID: <FC3DABDF-FA97-4E45-84C0-D9554669FF15@linaro.org> (raw)
In-Reply-To: <1481933536-12844-8-git-send-email-axboe@fb.com>
> Il giorno 17 dic 2016, alle ore 01:12, Jens Axboe <axboe@fb.com> ha scritto:
>
> This is basically identical to deadline-iosched, except it registers
> as a MQ capable scheduler. This is still a single queue design.
>
> Signed-off-by: Jens Axboe <axboe@fb.com>
...
> +
> +static void dd_merged_requests(struct request_queue *q, struct request *req,
> + struct request *next)
> +{
> + /*
> + * if next expires before rq, assign its expire time to rq
> + * and move into next position (next will be deleted) in fifo
> + */
> + if (!list_empty(&req->queuelist) && !list_empty(&next->queuelist)) {
> + if (time_before((unsigned long)next->fifo_time,
> + (unsigned long)req->fifo_time)) {
> + list_move(&req->queuelist, &next->queuelist);
> + req->fifo_time = next->fifo_time;
> + }
> + }
> +
Jens,
while trying to imagine the possible causes of Bart's hang with
bfq-mq, I've bumped into the following doubt: in the above function
(in my case, in bfq-mq-'s equivalent of the above function), are
we sure that neither req or next could EVER be in dd->dispatch instead
of dd->fifo_list? I've tried to verify it, but, although I think it has never
happened in my tests, I was not able to make sure that no unlucky
combination may ever happen (considering also the use of
blk_rq_is_passthrough too, to decide where to put a new request).
I'm making a blunder, right?
Thanks,
Paolo
next prev parent reply other threads:[~2017-02-16 10:46 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-17 0:12 [PATCHSET v4] blk-mq-scheduling framework Jens Axboe
2016-12-17 0:12 ` [PATCH 1/8] block: move existing elevator ops to union Jens Axboe
2016-12-17 0:12 ` [PATCH 2/8] blk-mq: make mq_ops a const pointer Jens Axboe
2016-12-17 0:12 ` [PATCH 3/8] block: move rq_ioc() to blk.h Jens Axboe
2016-12-20 10:12 ` Paolo Valente
2016-12-20 15:46 ` Jens Axboe
2016-12-20 22:14 ` Jens Axboe
2016-12-17 0:12 ` [PATCH 4/8] blk-mq: un-export blk_mq_free_hctx_request() Jens Axboe
2016-12-17 0:12 ` [PATCH 5/8] blk-mq: export some helpers we need to the scheduling framework Jens Axboe
2016-12-17 0:12 ` [PATCH 6/8] blk-mq-sched: add framework for MQ capable IO schedulers Jens Axboe
2016-12-20 11:55 ` Paolo Valente
2016-12-20 15:45 ` Jens Axboe
2016-12-21 2:22 ` Jens Axboe
2016-12-22 15:20 ` Paolo Valente
2016-12-22 9:59 ` Paolo Valente
2016-12-22 11:13 ` Paolo Valente
2017-01-17 2:47 ` Jens Axboe
2017-01-17 10:13 ` Paolo Valente
2017-01-17 12:38 ` Jens Axboe
2016-12-23 10:12 ` Paolo Valente
2017-01-17 2:47 ` Jens Axboe
2017-01-17 9:17 ` Paolo Valente
2016-12-17 0:12 ` [PATCH 7/8] mq-deadline: add blk-mq adaptation of the deadline IO scheduler Jens Axboe
2016-12-20 9:34 ` Paolo Valente
2016-12-20 15:46 ` Jens Axboe
2016-12-21 11:59 ` Bart Van Assche
2016-12-21 14:22 ` Jens Axboe
2016-12-22 16:07 ` Paolo Valente
2017-01-17 2:47 ` Jens Axboe
2016-12-22 16:49 ` Paolo Valente
2017-01-17 2:47 ` Jens Axboe
2017-01-20 11:07 ` Paolo Valente
2017-01-20 14:26 ` Jens Axboe
2017-01-20 13:14 ` Paolo Valente
2017-01-20 13:18 ` Paolo Valente
2017-01-20 14:28 ` Jens Axboe
2017-01-20 14:28 ` Jens Axboe
2017-02-01 11:11 ` Paolo Valente
2017-02-02 5:19 ` Jens Axboe
2017-02-02 9:19 ` Paolo Valente
2017-02-02 15:30 ` Jens Axboe
2017-02-02 21:15 ` Paolo Valente
2017-02-02 21:32 ` Jens Axboe
2017-02-07 17:27 ` Paolo Valente
2017-02-01 11:56 ` Paolo Valente
2017-02-02 5:20 ` Jens Axboe
2017-02-16 10:46 ` Paolo Valente [this message]
2017-02-16 15:35 ` Jens Axboe
2016-12-17 0:12 ` [PATCH 8/8] blk-mq-sched: allow setting of default " Jens Axboe
2016-12-19 11:32 ` [PATCHSET v4] blk-mq-scheduling framework Paolo Valente
2016-12-19 15:20 ` Jens Axboe
2016-12-19 15:33 ` Jens Axboe
2016-12-19 18:21 ` Paolo Valente
2016-12-19 21:05 ` Jens Axboe
2016-12-22 15:28 ` Paolo Valente
2017-01-17 2:47 ` Jens Axboe
2017-01-17 10:49 ` Paolo Valente
2017-01-18 16:14 ` Paolo Valente
2017-01-18 16:21 ` Jens Axboe
2017-01-23 17:04 ` Paolo Valente
2017-01-23 17:42 ` Jens Axboe
2017-01-25 8:46 ` Paolo Valente
2017-01-25 16:13 ` Jens Axboe
2017-01-26 14:23 ` Paolo Valente
2016-12-22 16:23 ` Bart Van Assche
2016-12-22 16:52 ` Omar Sandoval
2016-12-22 16:57 ` Bart Van Assche
2016-12-22 17:12 ` Omar Sandoval
2016-12-22 17:39 ` Bart Van Assche
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