Re: [PATCH 01 of 12] Core of mmu notifiers

[Robin Holt <holt@sgi.com>]

> I however doubt this will bring us back to the same performance of the
> current spinlock version, as the real overhead should come out of
> overscheduling in down_write ai anon_vma_link. Here an initially
> spinning lock would help but that's gray area, it greatly depends on
> timings, and on very large systems where a cacheline wait with many
> cpus forking at the same time takes more than scheduling a semaphore
> may not slowdown performance that much. So I think the only way is a
> configuration option to switch the locking at compile time, then XPMEM
> will depend on that option to be on, I don't see a big deal and this
> guarantees embedded isn't screwed up by totally unnecessary locks on UP.

You have said this continually about a CONFIG option.  I am unsure how
that could be achieved.  Could you provide a patch?

Thanks,
Robin