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Subject: Re: svn commit: r242402 - in head/sys: kern vm
From: Ian Lepore <freebsd@damnhippie.dyndns.org>
To: attilio@FreeBSD.org
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Date: Thu, 01 Nov 2012 08:01:12 -0600
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Cc: svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org,
 Gleb Smirnoff <glebius@FreeBSD.org>, src-committers@FreeBSD.org
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On Thu, 2012-11-01 at 10:42 +0000, Attilio Rao wrote:
> On 11/1/12, Gleb Smirnoff <glebius@freebsd.org> wrote:
> > On Wed, Oct 31, 2012 at 06:33:51PM +0000, Attilio Rao wrote:
> > A> > Doesn't this padding to cache line size only help x86 processors in an
> > A> > SMP kernel?  I was expecting to see some #ifdef SMP so that we don't
> > pay
> > A> > a big price for no gain in small-memory ARM systems and such.  But
> > maybe
> > A> > I'm misunderstanding the reason for the padding.
> > A>
> > A> I didn't want to do this because this would be meaning that SMP option
> > A> may become a completely killer for modules/kernel ABI compatibility.
> >
> > Do we support loading non-SMP modules on SMP kernel and vice versa?
> 
> Actually that's my point, we do.
> 
> Attilio
> 
> 

Well we've got other similar problems lurking then.  What about a module
compiled on an arm system that had #define CACHE_LINE_SIZE 32 and then
it gets run on a different arm system whose kernel is compiled with
#define CACHE_LINE_SIZE 64?

-- Ian