Messages in this thread | | | Date | Fri, 21 Nov 2014 15:19:28 +0800 | From | zhanghailiang <> | Subject | Re: [PATCH 00/17] RFC: userfault v2 |
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On 2014/11/21 1:38, Andrea Arcangeli wrote: > Hi, > > On Thu, Nov 20, 2014 at 10:54:29AM +0800, zhanghailiang wrote: >> Yes, you are right. This is what i really want, bypass all non-present faults >> and only track strict wrprotect faults. ;) >> >> So, do you plan to support that in the userfault API? > > Yes I think it's good idea to support wrprotect/COW faults too. >
Great! Then i can expect your patches. ;)
> I just wanted to understand if there was any other reason why you > needed only wrprotect faults, because the non-present faults didn't > look like a big performance concern if they triggered in addition to > wrprotect faults, but it's certainly ok to optimize them away so it's > fully optimal. >
Er, you have got the answer, no special, it's only for optimality.
> All it takes to differentiate the behavior should be one more bit > during registration so you can select non-present, wrprotect faults or > both. postcopy live migration would select only non-present faults, > postcopy live snapshot would select only wrprotect faults, anything > like distributed shared memory supporting shared readonly access and > exclusive write access, would select both flags. >
It is really flexible in this way.
> I just sent an (unfortunately) longish but way more detailed email > about live snapshotting with userfaultfd but I just wanted to give a > shorter answer here too :). >
Thanks for your explanation, and your patience. It is really useful, now i know more details about why 'fork & dump live snapshot' scenario is not acceptable. Thanks :)
> Thanks, > Andrea > > . >
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