[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] libxc: try to find last used pfn when migrating
On 27/11/15 16:01, David Vrabel wrote: > On 27/11/15 14:50, Juergen Gross wrote: >> For migration the last used pfn of a guest is needed to size the >> logdirty bitmap and as an upper bound of the page loop. Unfortunately >> there are pv-kernels advertising a much higher maximum pfn as they >> are really using in order to support memory hotplug. This will lead >> to allocation of much more memory in Xen tools during migration as >> really needed. >> >> Try to find the last used guest pfn of a pv-domu by scanning the p2m >> tree from the last entry towards it's start and search for an entry >> not being invalid. >> >> Normally the mid pages of the p2m tree containing all invalid entries >> are being reused, so we can just scan the top page for identical >> entries and skip them but the first one. > > This has been fixed in Linux by "x86/xen/p2m: hint at the last populated > P2M entry" 98dd166ea3a3c3b57919e20d9b0d1237fcd0349d which is tagged for > stable. > > Do we really need a toolstack fix as well? xl migrate will use much less resources for a domain with a 3.x kernel started with max_mem being much larger than mem. E.g. in case you start a domain on a small stand-by system and migrate it later to the large production system and want to balloon it up there. Additionally there was a discussion this week on irc regarding this topic and concern was raised this could block dom0 responsiveness. Juergen _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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