On Tue, Jun 20, 2017 at 06:49:33PM +0200, David Hildenbrand wrote: > On 20.06.2017 18:44, Rik van Riel wrote: > > On Mon, 2017-06-12 at 07:10 -0700, Dave Hansen wrote: > > > >> The hypervisor is going to throw away the contents of these pages, > >> right? As soon as the spinlock is released, someone can allocate a > >> page, and put good data in it. What keeps the hypervisor from > >> throwing > >> away good data? > > > > That looks like it may be the wrong API, then? > > > > We already have hooks called arch_free_page and > > arch_alloc_page in the VM, which are called when > > pages are freed, and allocated, respectively. > > > > Nitesh Lal (on the CC list) is working on a way > > to efficiently batch recently freed pages for > > free page hinting to the hypervisor. > > > > If that is done efficiently enough (eg. with > > MADV_FREE on the hypervisor side for lazy freeing, > > and lazy later re-use of the pages), do we still > > need the harder to use batch interface from this > > patch? > > > David's opinion incoming: > > No, I think proper free page hinting would be the optimum solution, if > done right. This would avoid the batch interface and even turn > virtio-balloon in some sense useless. I agree generally. But we have to balance that against the fact that this was discussed since at least 2011 and no one built this solution yet. > -- > > Thanks, > > David
