svn commit: r242402 - in head/sys: kern vm
Adrian Chadd
adrian at freebsd.org
Wed Oct 31 18:50:18 UTC 2012
On 31 October 2012 11:33, Attilio Rao <attilio at freebsd.org> wrote:
>> Doesn't this padding to cache line size only help x86 processors in an
>> SMP kernel? I was expecting to see some #ifdef SMP so that we don't pay
>> a big price for no gain in small-memory ARM systems and such. But maybe
>> I'm misunderstanding the reason for the padding.
>
> I didn't want to do this because this would be meaning that SMP option
> may become a completely killer for modules/kernel ABI compatibility.
Right, but you didn't make it configurable for us embedded peeps who
still care about memory usage.
> Also, if you look at the modified list of locks I don't think they
> should be too much, I hardly believe ARM UP is going to hurt that much
> from loosing some padding in tdq structures or callout.
There's a few million more embedded MIPS boards out there with
16mb/32mb of RAM than target PCs for FreeBSD.
Would you mind making the padding part configurable and just default
it to "do the padding" ?
That way for the atheros MIPS builds I can turn it off and save on the
memory overhead.
Thanks,
Adrian
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