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[Xen-devel] Re: [PATCH 1 of 4] mm: add a ptep_modify_prot transaction abstraction

Benjamin Herrenschmidt wrote:
On Wed, 2008-06-18 at 17:24 -0700, Linus Torvalds wrote:
On Wed, 18 Jun 2008, Jeremy Fitzhardinge wrote:
Along the lines of:
Hell no. There's a reason we have a special set_wrprotect() thing. We can do it more efficiently on native hardware by just clearing the bit atomically. No need to do the cmpxchg games.

But we can't batch ...

Which architecture are you interested in? If it isn't x86, you can probably get anything past Linus ;)

I'll do some measurements to see what effect the batchable ptep_set_wrprotect() has on native. If it's significant, I'll propose making it conditional on CONFIG_PARAVIRT.


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