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

[Jay Lan]

You are right, Jens. In our earlier posting, we also included block
device read/write counters. The block read/write counts are not very
accurate but it fits our customers' needs since they used that
information sort of for performance analysis than for accounting
purpose.

Thus the block read/write counters were removed from our patch so
that we can concentrate on the accounting needs. This bwtime (block
wait time) should have been pulled together with block read/write
counters.

Regards,
 - jay


Jens Axboe wrote:
> 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.
>  

-
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