hi george >Please don't cross-post unless you need to. These are coding >questions, so xen-devel is the right place to ask this. > >On Thu, Apr 28, 2016 at 7:58 AM, Zhang, Chunyu <zhan...@cn.fujitsu.com> wrote: >> >> hi all >> >> i have two question about ballon. >> >> 1. >> cfg: >> memory=4096 >> maxmem=4096 >> >> no pod was set , no balloon is set . >> when xl create, i find function decrease_reservation is call. >> i did not why ? > >decrease_reservation is never initiated by the hypervisor -- it's >normally initiated by the guest balloon driver; although I think it >may also be initiated by other components, like hvmloader or qemu (not >sure about that). You'd have to figure out which component was making >that hypercall, and then look in the logic to find out why it was >doing so. got it. i will check it. > >> >> 2. pod + balloon >> cfg: >> memory=512 >> maxmem=4096 >> >> decrease_reservation >> - p2m_pod_decrease_reservation >> - p2m_set_entry(p2m_invalid) >> - guest_remove_page >> - p2m_set_entry(p2m_invalid) >> >> in p2m_pod_decrease_reservation , gfn entry is set p2c_invalid. >> but in guest_remove_page gfn entry is set p2c_invalid again. >> i did not know why? > >Did you not notice the "continue" between >p2m_pod_decrease_reservation() and guest_remove_page()? :-) oh.... i know the point(âīšâ)b > >p2m_pod_decrease_reservation() either does everything necessary (both >reclaim the page and set the p2m entry) or nothing. It will return 0 >to mean, "I didn't do anything, you still need to free the page", and >1 to mean "I did everything, no need for you to do anything more." got it, thank u very much. > > -George > >
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