Thanks! What kind if obstacles would I face if I tried to implemented the same behavior (Scan processes) for Linux guests? I plan on scanning every process then check the memory maps from /proc/<pid>/maps. If the permissions are set to r only or rx then I'll register the pages with the host. This wouldn't cover the process it self, but a major portion of the wasted memory.
Sounds simple (everything does these days) and I plan to work it. However, I just need an expert to give me the go-ahead since this is all new to me. Thanks, Ribhi On Fri, Apr 13, 2012 at 6:41 PM, Alexey Eromenko <[email protected]> wrote: > > The guest additions service scans the guest for modules (user/kernel) and > > registers each module with the hypervisor on the host. Then notifies the > > hypervisor to check if the pages are shared with other VMs. What I don't > > understand is what happens when the hypervisor decides that two pages are > > the same? And what happens if one of these pages change *after* it was > > already "merged" with other similar pages. > > AFAIK if two pages are the same, only one is stored in RAM, with 2 > references from 2 VMs (or 2 references from same 1 VM, deduplicating > mem inside 1 VM). > If one VM changes page, it just copied to new location, so now VBox > stops deduping this page. > This is how KSM works, and how I expect PageFusion to work. > > > And ,sorry to ask this, is KSM utilized when it is enabled on the host? > > Of course not. > VBox is cross-platform technology, while KSM is Linux only, so KSM is > useless for VBox. > One advantage of KSM, is that it doesn't depend on any guest drivers, > and all logic is done host-side. VBox PageFusing requires GA, > Guest-OS-specific drivers. > But I didn't done any benchmarking to compare the efficiency of both > approaches. > -- > -Alexey Eromenko "Technologov" > > _______________________________________________ > vbox-dev mailing list > [email protected] > https://www.virtualbox.org/mailman/listinfo/vbox-dev > -- -- Ribhi
_______________________________________________ vbox-dev mailing list [email protected] https://www.virtualbox.org/mailman/listinfo/vbox-dev
