Re: DragonFly-2.3.0.828.gd7215 master sys/dev/netif/emx if_emx.h

["Simon 'corecode' Schubert" <corecode@xxxxxxxxxxxx>]

Sepherosa Ziehau wrote:
> On Wed, Apr 29, 2009 at 9:42 AM, Matthew Dillon
> <dillon@apollo.backplane.com> wrote:
> > :Yeah.  However, could you tell me the major reason you want to put
> > :__cachealign in struct field?  I guess you worried about emx_rxdata
> > :being used outside of emx_softc?
> >    It's more obvious that the array needs to be cache-aligned if it is
> >    in the softc structure.  Also, it's more C-like.  Putting storage
> >    attributes on structural definitions is not very C-like.  The storage
> >    attributes should be on declarations instead.
>
> Mmm, setting __cachealign on struct field (i.e. in emx_softc) does not
> achieve what I want here: I want the struct's size to be (N *
> cacheline_size) in addition to be cacheline_size aligned.  So in
> ifpoll, CPU0's writing to rx_data[0] will not pollute rx_data[1]'s
> cache in CPU1.

Right.  Every array element needs to be cache aligned, not only the array by itself.

cheers
 simon