svn commit: r242402 - in head/sys: kern vm

[Attilio Rao]

On Thu, Nov 1, 2012 at 2:01 PM, Ian Lepore
<freebsd at damnhippie.dyndns.org> wrote:
> On Thu, 2012-11-01 at 10:42 +0000, Attilio Rao wrote:
>> On 11/1/12, Gleb Smirnoff <glebius at 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?

That should not happen. Is that a real case where you build a module
for an ARM family and want to run against a kernel compiled for
another?

CACHE_LINE_SIZE must not change during a STABLE release lifetime, of
course, for the same arch.

Attilio


-- 
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