lkml.org 
[lkml]   [2007]   [May]   [9]   [last100]   RSS Feed
Views: [more markup]  [less markup]  [headers]  [forward] 
 
Messages in this thread
/
DateWed, 9 May 2007 08:49:23 +0200
FromJens Axboe <>
SubjectRe: [2.6.22 PATCH 22/26] dm: bio list helpers
On Tue, May 08 2007, Andrew Morton wrote:
> >  static inline void bio_list_init(struct bio_list *bl)
> >  {
> >  	bl->head = bl->tail = NULL;
> >  }
> > 
> > +#define bio_list_for_each(bio, bl) \
> > +	for (bio = (bl)->head; bio && ({ prefetch(bio->bi_next); 1; }); \
> > +	     bio = bio->bi_next)
> > +
> 
> I have this vague memory from a long time ago that one particular CPU type
> wants to go oops when prefetching from an invalid address.
> 
> Maybe that went away for some reason - we'd have hit it again if it was
> real.

Besides, manual prefetching is very rarely a win. I dabbled with some
benchmarks a few weeks back (with the doubly linked lists), and in most
cases it was actually a loss. So I'd vote for just removing the
prefetch() above.

-- 
Jens Axboe

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2007-05-09 06:55    [from the cache]
©2003-2008