[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] RE: [Xen-devel] write page table in user mode
Just now I made a conclusion that no such unshadow heuristic is hit after checking my archived perfc counter logs, since there's no item like "unshadow by user-level access". But immediately I found this is mixed into "emulator fails", and there does be dozens of count for Linux KB and several for one Windows benchmark (not sure the detail now). Whatever the count may be, even one user page slipped out of unshadow may hurt performance a lot if access to that page is frequent... Maybe we can disable such heuristics only when observing guest clear CR0.wp actively? Or later out-of-sync can also help here. BTW, it's worthy of adding a seperate perfc counter for user-level access caused unshadow. :-) Thanks, kevin >From: Keir Fraser >Sent: 2008年2月2日 18:31 > >It should be safe, but I don't know how much it would affect >performance (it >depends on how much we are actually relying on it as an unshadowing >heuristic). > > -- Keir > >On 1/2/08 18:28, "Su, Disheng" <disheng.su@xxxxxxxxx> wrote: > >> Hi, >> I found vmware workstation 5 in xen will write page table in >> user mode. I don't know the rational behind this... >> XEN doesn't emulate writing page table in user mode. If I get >> rid of this constraint, vmware will go a little bit further. >> Is it safe to remove this constraint? >> >> Best Regards, >> Disheng, Su >> >> _______________________________________________ >> Xen-devel mailing list >> Xen-devel@xxxxxxxxxxxxxxxxxxx >> http://lists.xensource.com/xen-devel > > > >_______________________________________________ >Xen-devel mailing list >Xen-devel@xxxxxxxxxxxxxxxxxxx >http://lists.xensource.com/xen-devel > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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