Re: [RFC][PATCH] net drivers and cache alignment

[Andrew Morton <akpm@digeo.com>]

Andrew Morton wrote:
> 
> "David S. Miller" wrote:
> >
> >    From: Andrew Morton <akpm@digeo.com>
> >    Date: Sat, 07 Dec 2002 15:29:16 -0800
> >
> >    Jeff Garzik wrote:
> >    > Attached is cut #2.  Thanks for all the near-instant feedback so far :)
> >    >   Andrew, does the attached still need padding on SMP?
> >
> >    It needs padding _only_ on SMP.  ____cacheline_aligned_in_smp.
> >
> > non-smp machines lack L2 caches?  That's new to me :-)
> >
> > More seriously, there are real benefits on non-SMP systems.
> 
> Then I am most confused.  None of these fields will be put under
> busmastering or anything like that, so what advantage is there in
> spreading them out?

Oh I see what you want - to be able to pick up all the operating fields
in a single fetch.

That will increase the overall cache footprint though.  I wonder if
it's really a net win, over just keeping it small.