Re: [PATCH 2.6.9-rc2 1/2] enhanced I/O accounting data collection

[Jens Axboe]

Hi,

> Index: linux/drivers/block/ll_rw_blk.c
> ===================================================================
> --- linux.orig/drivers/block/ll_rw_blk.c	2004-09-12 22:31:31.000000000 -0700
> +++ linux/drivers/block/ll_rw_blk.c	2004-09-27 12:37:04.374234677 -0700
> @@ -1741,6 +1741,7 @@
> {
> 	DEFINE_WAIT(wait);
> 	struct request *rq;
>+	unsigned long start_wait = jiffies;
> 
> 	generic_unplug_device(q);
> 	do {
>@@ -1769,6 +1770,7 @@
> 		finish_wait(&rl->wait[rw], &wait);
> 	} while (!rq);
> 
>+	current->bwtime += (unsigned long) jiffies - start_wait;
> 	return rq;
> }

What is the purpose of this hunk alone as block io accounting? It
doesn't make any sense to me - you are accounting the time a process
spends sleeping on a congested queue, it has nothing to do with the
bandwidth time it used. Which, btw, isn't so easy to account on queueing
hardware.

Just curious on what you are trying to achieve here.
 
-- 
Jens Axboe

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