Re: [PATCH] blk queue io tracing support

[Nathan Scott <nathans@sgi.com>]

On Tue, Aug 23, 2005 at 02:32:36PM +0200, Jens Axboe wrote:
> Hi,
> 
> This is a little something I have played with. It allows you to see
> exactly what is going on in the block layer for a given queue. Currently
> it can logs request queueing and building, dispatches, requeues, and
> completions.

Ah, fabulous.  Thanks Jens!

> +	t.magic		= BLK_IO_TRACE_MAGIC | BLK_IO_TRACE_VERSION;
> +	t.sequence	= atomic_add_return(1, &bt->sequence);
> +	t.time		= sched_clock() / 1000;

Wouldn't it be better to pass out the highest precision available here
& then do the conversion in userspace instead?  I guess one might want
that little bit more for a RAM disk or something ... actually, talking
to one of the SGI people here with alot of experience on IRIX with a
similar facility, the msec resolution there is apparently sometimes an
issue already with fast storage.

cheers.

-- 
Nathan