Re: [RFC] kernel facilities for cache prefetching

[Diego Calleja <diegocg@gmail.com>]

El Wed, 03 May 2006 17:39:51 -0600,
Zan Lynx <zlynx@acm.org> escribió:

> Linux should be able to do something like this using unionfs.  It could
> be worthwhile to try it with one of the very fastest flash cards or USB
> drives.

BTW; I forgot that the next intel laptops (and apparently, mactel laptops)
will have a small flash memory built in for this very purpose. According
to an article at extremetech.com, the flash memory requires an "I/O
controller"; IOW, it is not transparent and seems to need support from the
OS (although I guess that vista's "superprefetch" was designed precisely
for this hardware). Apparently, the main purpose here is to improve the
battery life (disks seeking for too many seconds can eat lot of power,
I guess). "Prefetchers" are becoming trendy, it seems

(page 14) http://www.intel.com/pressroom/kits/events/idfspr_2006/20060307_MaloneyTranscript.pdf

> With slower cards and USB keys its more of a loss unless the faster seek
> speed can make up for it, because sequential hard drive access is
> faster.

That's where the gain is; if the hard drive access was sequential people
wouldn't be talking about prefetchers. My SATA desktop drive also does
~45 MB/s, but it doesn't goes beyond 2 when seeking