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 :)
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