Re: [libvirt] [PATCH v2 3/7] virnuma: Introduce pages helpers

On Mon, Jun 16, 2014 at 05:08:26PM +0200, Michal Privoznik wrote: > +int > +virNumaGetPageInfo(int node, > + unsigned int page_size, > + unsigned int *page_avail, > + unsigned int *page_free) > +{ > + int ret = -1; > + long system_page_size = sysconf(_SC_PAGESIZE); > + > + /* sysconf() returns page size in bytes, > + * the @page_size is however in kibibytes */ > + if (page_size == system_page_size / 1024) { > + unsigned long long memsize, memfree; > + > + /* TODO: come up with better algorithm that takes huge pages into > + * account. The problem is huge pages cut off regular memory. */ Hmm, so this code is returning normal page count that ignores the fact that some pages are not in fact usable because they've been stolen for huge pages ? I was thinking that the total memory reported by the kernel was reduced when you allocated huage pages, but testing now, it seems I was mistaken in that belief. So this is a bit of a nasty gotcha because a user of this API would probably expect that the sum of page size * page count for all page sizes would equal total physical RAM (give or take). I still like the idea of including the default page size in this info, but perhaps we should disable the default system page size for now & revisit later if we can figure out a way to accurately report it, rather than reporting misleading info.