got it. thanks On Fri, Jul 11, 2008 at 12:50 AM, Izik Eidus <[EMAIL PROTECTED]> wrote: > ציטוט Sukanto Ghosh: >>>> >>>> Doesn't KSM notifies KVM about the shared pages so that KVM can update >>>> its sptes accordingly or is it done by KSM itself ? >>>> >>>> >>> >>> when using kvm, mmu notifiers is a must for ksm, (mmu notifiers update >>> kvm >>> about the changes in the host page table) >>> >>> >>>> >>>> What about KSM being used by someone other than KVM ? Does KSM updates >>>> the ptes of the shared pages itself ? >>>> >>>> >>> >>> it can be used by any application, it update the ptes of the host, what >>> you >>> mean by the shared pages itself? >>> >> >> by "itself" I meant 'ksm'. So ksm will take care of updating the ptes >> of the shared guest pages. >> > > yes > >> >> >>>> >>>> >>>>>> >>>>>> Where are the shared pages kept ? In kernel memory ? Aren't the shared >>>>>> pages always pinned in RAM (due to same reasons for pinned shadowed >>>>>> pages) ? >>>>>> >>>>>> >>>>>> >>>>> >>>>> in the version that was sent to the list it was kernel memory (meaning >>>>> shared pages are not swappable >>>>> (just the pages that are shared not the pages that we scan, when they >>>>> are >>>>> split beacuse of copy on write it become swappable again >>>>> new version that i will send soon the pages are normal >>>>> anonymous/userspace >>>>> memory that is swappable >>>>> >>>>> >>>>> >>>> >>>> What is the strategy/method which you will use to represent the shared >>>> memory as normal anonymous/userspace memory ? Then, these pages must >>>> be staying at one of the guest's address-space (whose pages have been >>>> shared) ? >>>> >>>> >>> >>> it possible due to another patch that i need to send, that allow modules >>> register new reverse mapping call backs..., >>> >>> >> >> ok >> >> but in whose address-space will these shared pages stay ? >> >> > > if we have 5 applications sharing the same page, we will have the page stay > in 5 diffrent address-spaces... > >> >>>> >>>> >>>>>> >>>>>> How much is the overhead involved due to this ? >>>>>> >>>>>> >>>>>> >>>>> >>>>> depeand on the speed you tell it to scan, but the overhead is about ~5% >>>>> for >>>>> common cases >>>>> >>>>> >>>> >>>> Can I know the typical values of the parameters : sleep time, no. of >>>> pages to scan, which you used to arrive at the above mentioned >>>> overhead. >>>> >>>> >>> >>> i think it is about 256 2000 (256 pages per 2000 usleep) >>> (note that most of the cpu is acutlay taken by the copying of the pages >>> when >>> a new shared page is created, i have possible way to change it and reduce >>> the cpu even more >>> but i dont know if i want to do it) (it add more IFs to the fast path >>> inside >>> the mm) >>> >>> >>> >>>> >>>> >>> >>> >> >> Thanks :) >> >> > >
-- Regards, Sukanto Ghosh
