Re: [libvirt] [Xen-devel] libvirt/libxl implemetation of get_online_cpu / virNodeGetCPUMap?

On Tue, 2015-02-24 at 13:10 +0000, Ian Campbell wrote: > On Tue, 2015-02-24 at 12:41 +0000, Anthony PERARD wrote: > > What libxl API those provide this information, if it exist? > > > > I found libxl_get_online_cpus() but that not enough. They want a > > bitmap. > > I think that is all which currently exists, at least at the libxl level, > you may need to add a new interface. > > It'd be worth looking into the various host numa interfaces -- perhaps > one of them indirectly exposes what you want? > Given Daniel's latest emails, I'm not sure this is useful but libxl_get_cpu_topology() should put LIBXL_CPUTOPOLOGY_INVALID_ENTRY in all the fields of the i-eth element of the array it returns, if the i-eth pcpu is offline (see the implementation of XEN_SYSCTL_topologyinfo in xen/common/sysctl.c). So, scanning that array and constructing the bitmap according to whether or not we find that marker on the various elements would be the way to go, I would say. I've actually never tested this, i.e., I've never tried offlining a pcpu on the host. I'll give it a go as soon as I find 5 minutes, and let know if it works.