Re: [Patch for review] BSD accounting IO stats

[Andi Kleen]

Guillaume Thouvenin <guillaume.thouvenin@xxxxxxxx> writes:

> diff -uprN -X dontdiff linux-2.6.8-rc2/drivers/block/ll_rw_blk.c linux-2.6.8-rc2+BSDacct_IO/drivers/block/ll_rw_blk.c
> --- linux-2.6.8-rc2/drivers/block/ll_rw_blk.c	2004-07-18 06:57:42.000000000 +0200
> +++ linux-2.6.8-rc2+BSDacct_IO/drivers/block/ll_rw_blk.c	2004-07-27 09:17:33.149321480 +0200
> @@ -1949,10 +1949,12 @@ void drive_stat_acct(struct request *rq,
>  
>  	if (rw == READ) {
>  		disk_stat_add(rq->rq_disk, read_sectors, nr_sectors);
> +		current->rblk += nr_sectors;

This doesn't look very useful, because most writes which
are flushed delayed would get accounted to pdflushd.
Using such inaccurate data for accounting sounds quite dangerous
to me.

If you really wanted to do this i guess you would need to 
track the pid of the process and account it there. But the
process may be already gone, so it would better fit into
some other longer lived data structure (like the uid) 

Overall I don't think this accounting is worth it because
doing it right would be quite some overhead and doing it in
a simple way like this patch is too inaccurate.

-Andi

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