linux-kernel - Re: [PATCH] Fix discard requests accounting in the diskstats

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Date:	Fri, 17 Apr 2009 08:49:12 +0200
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Nikanth Karthikesan <knikanth@...e.de>
Cc:	David Woodhouse <David.Woodhouse@...el.com>,
	linux-kernel@...r.kernel.org, jmarchan@...hat.com
Subject: Re: [PATCH] Fix discard requests accounting in the diskstats

On Fri, Apr 17 2009, Nikanth Karthikesan wrote:
> When 2 discard requests are merged, the stats gets updated, but we do not
> update statistics normally when a discard request is issued or completed. For
> example the in_flight counter would be decremented when 2 discard requests are
> merged, but it was not at all incremented when they were issued, and in_flight
> counter will not be decremented, when they are completed as well.
> 
> This patch fixes this by adding discard requests to the statistics.

This needs rebasing on top of this one:

http://lkml.org/lkml/2009/4/16/159

whenever that gets resubmitted as a proper, working patch.

> 
> Signed-off-by: Nikanth Karthikesan <knikanth@...e.de>
> 
> ---
> 
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 07ab754..ee960a7 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -68,7 +68,7 @@ static void drive_stat_acct(struct request *rq, int new_io)
>  	int rw = rq_data_dir(rq);
>  	int cpu;
>  
> -	if (!blk_fs_request(rq) || !blk_do_io_stat(rq))
> +	if (!rq_accountable(rq) || !blk_do_io_stat(rq))
>  		return;
>  
>  	cpu = part_stat_lock();
> @@ -1698,7 +1698,7 @@ static void blk_account_io_done(struct request *req)
>  	 * IO on queueing nor completion.  Accounting the containing
>  	 * request is enough.
>  	 */
> -	if (blk_fs_request(req) && req != &req->q->bar_rq) {
> +	if (rq_accountable(req) && req != &req->q->bar_rq) {
>  		unsigned long duration = jiffies - req->start_time;
>  		const int rw = rq_data_dir(req);
>  		struct hd_struct *part;
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index ba54c83..9483c02 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -667,7 +667,9 @@ static inline void blk_clear_queue_full(struct request_queue *q, int sync)
>  	(REQ_NOMERGE | REQ_STARTED | REQ_HARDBARRIER | REQ_SOFTBARRIER)
>  #define rq_mergeable(rq)	\
>  	(!((rq)->cmd_flags & RQ_NOMERGE_FLAGS) && \
> -	 (blk_discard_rq(rq) || blk_fs_request((rq))))
> +	 (blk_discard_rq(rq) || blk_fs_request(rq)))
> +#define rq_accountable(rq)	\
> +	(blk_discard_rq(rq) || blk_fs_request(rq))
>  
>  /*
>   * q->prep_rq_fn return values
> 

-- 
Jens Axboe

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