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DateWed, 18 Jun 2008 22:03:43 -0700
FromJeremy Fitzhardinge <>
SubjectRe: [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.

    J


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