linux-kernel - Re: [PATCH v9 3/4] block: implement runtime pm strategy

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Message-ID: <20130219022900.GA2285@aaronlu.sh.intel.com>
Date:	Tue, 19 Feb 2013 10:29:00 +0800
From:	Aaron Lu <aaron.lu@...el.com>
To:	Alan Stern <stern@...land.harvard.edu>
Cc:	Jens Axboe <axboe@...nel.dk>, "Rafael J. Wysocki" <rjw@...k.pl>,
	James Bottomley <James.Bottomley@...senpartnership.com>,
	linux-pm@...r.kernel.org, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-ide@...r.kernel.org,
	Aaron Lu <aaron.lwe@...il.com>,
	Shane Huang <shane.huang@....com>
Subject: Re: [PATCH v9 3/4] block: implement runtime pm strategy

Hi Alan,

On Tue, Feb 05, 2013 at 04:03:15PM +0800, Aaron Lu wrote:
> From: Lin Ming <ming.m.lin@...el.com>
> 
> When a request is added:
>     If device is suspended or is suspending and the request is not a
>     PM request, resume the device.
> 
> When the last request finishes:
>     Call pm_runtime_mark_last_busy().
> 
> When pick a request:
>     If device is resuming/suspending, then only PM request is allowed
>     to go.

I think I should add the following words in patch 2 & 3's changelog:

The idea and API is designed by Alan Stern and described here:
http://marc.info/?l=linux-scsi&m=133727953625963&w=2

to reflect your credit if you don't object.

Please let me know what do you think, or if there is a better way to
reflect this, please feel free to let me know.

Thanks,
Aaron

> 
> Signed-off-by: Lin Ming <ming.m.lin@...el.com>
> Signed-off-by: Aaron Lu <aaron.lu@...el.com>
> ---
>  block/blk-core.c | 39 +++++++++++++++++++++++++++++++++++++++
>  block/elevator.c | 26 ++++++++++++++++++++++++++
>  2 files changed, 65 insertions(+)
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index ce7d366..81f173e 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -1264,6 +1264,16 @@ void part_round_stats(int cpu, struct hd_struct *part)
>  }
>  EXPORT_SYMBOL_GPL(part_round_stats);
>  
> +#ifdef CONFIG_PM_RUNTIME
> +static void blk_pm_put_request(struct request *rq)
> +{
> +	if (rq->q->dev && !(rq->cmd_flags & REQ_PM) && !--rq->q->nr_pending)
> +		pm_runtime_mark_last_busy(rq->q->dev);
> +}
> +#else
> +static inline void blk_pm_put_request(struct request *rq) {}
> +#endif
> +
>  /*
>   * queue lock must be held
>   */
> @@ -1274,6 +1284,8 @@ void __blk_put_request(struct request_queue *q, struct request *req)
>  	if (unlikely(--req->ref_count))
>  		return;
>  
> +	blk_pm_put_request(req);
> +
>  	elv_completed_request(q, req);
>  
>  	/* this is a bio leak */
> @@ -2051,6 +2063,28 @@ static void blk_account_io_done(struct request *req)
>  	}
>  }
>  
> +#ifdef CONFIG_PM_RUNTIME
> +/*
> + * Don't process normal requests when queue is suspended
> + * or in the process of suspending/resuming
> + */
> +static struct request *blk_pm_peek_request(struct request_queue *q,
> +					   struct request *rq)
> +{
> +	if (q->dev && (q->rpm_status == RPM_SUSPENDED ||
> +	    (q->rpm_status != RPM_ACTIVE && !(rq->cmd_flags & REQ_PM))))
> +		return NULL;
> +	else
> +		return rq;
> +}
> +#else
> +static inline struct request *blk_pm_peek_request(struct request_queue *q,
> +						  struct request *rq)
> +{
> +	return rq;
> +}
> +#endif
> +
>  /**
>   * blk_peek_request - peek at the top of a request queue
>   * @q: request queue to peek at
> @@ -2073,6 +2107,11 @@ struct request *blk_peek_request(struct request_queue *q)
>  	int ret;
>  
>  	while ((rq = __elv_next_request(q)) != NULL) {
> +
> +		rq = blk_pm_peek_request(q, rq);
> +		if (!rq)
> +			break;
> +
>  		if (!(rq->cmd_flags & REQ_STARTED)) {
>  			/*
>  			 * This is the first time the device driver
> diff --git a/block/elevator.c b/block/elevator.c
> index 11683bb..29c5c7e 100644
> --- a/block/elevator.c
> +++ b/block/elevator.c
> @@ -34,6 +34,7 @@
>  #include <linux/blktrace_api.h>
>  #include <linux/hash.h>
>  #include <linux/uaccess.h>
> +#include <linux/pm_runtime.h>
>  
>  #include <trace/events/block.h>
>  
> @@ -515,6 +516,27 @@ void elv_bio_merged(struct request_queue *q, struct request *rq,
>  		e->type->ops.elevator_bio_merged_fn(q, rq, bio);
>  }
>  
> +#ifdef CONFIG_PM_RUNTIME
> +static void blk_pm_requeue_request(struct request *rq)
> +{
> +	if (rq->q->dev && !(rq->cmd_flags & REQ_PM))
> +		rq->q->nr_pending--;
> +}
> +
> +static void blk_pm_add_request(struct request_queue *q, struct request *rq)
> +{
> +	if (q->dev && !(rq->cmd_flags & REQ_PM) && q->nr_pending++ == 0 &&
> +	    (q->rpm_status == RPM_SUSPENDED || q->rpm_status == RPM_SUSPENDING))
> +		pm_request_resume(q->dev);
> +}
> +#else
> +static inline void blk_pm_requeue_request(struct request *rq) {}
> +static inline void blk_pm_add_request(struct request_queue *q,
> +				      struct request *rq)
> +{
> +}
> +#endif
> +
>  void elv_requeue_request(struct request_queue *q, struct request *rq)
>  {
>  	/*
> @@ -529,6 +551,8 @@ void elv_requeue_request(struct request_queue *q, struct request *rq)
>  
>  	rq->cmd_flags &= ~REQ_STARTED;
>  
> +	blk_pm_requeue_request(rq);
> +
>  	__elv_add_request(q, rq, ELEVATOR_INSERT_REQUEUE);
>  }
>  
> @@ -551,6 +575,8 @@ void __elv_add_request(struct request_queue *q, struct request *rq, int where)
>  {
>  	trace_block_rq_insert(q, rq);
>  
> +	blk_pm_add_request(q, rq);
> +
>  	rq->q = q;
>  
>  	if (rq->cmd_flags & REQ_SOFTBARRIER) {
> -- 
> 1.8.1
> 
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