Re: [libvirt] "[V3] RFC for support cache tune in libvirt"

On Wed, Jan 11, 2017 at 10:19:10AM -0200, Marcelo Tosatti wrote: > > Hi, > > Comments/questions related to: > https://www.redhat.com/archives/libvir-list/2017-January/msg00354.html > > 1) root s2600wt:~/linux# virsh cachetune kvm02 --l3.count 2 > > How does allocation of code/data look like? > > 2) 'nodecachestats' command: > > 3. Add new virsh command 'nodecachestats': > This API is to expose vary cache resouce left on each hardware (cpu > socket). > It will be formated as: > <resource_type>.<resource_id>: left size KiB > > Does this take into account that only contiguous regions of cbm masks > can be used for allocations? > > Also, it should return the amount of free cache on each cacheid. > > 3) The interface should support different sizes for different > cache-ids. See the KVM-RT use case at > https://www.redhat.com/archives/libvir-list/2017-January/msg00415.html > "WHAT THE USER NEEDS TO SPECIFY FOR VIRTUALIZATION (KVM-RT)". And when the user specification lacks cacheid of a given socket in the system, the code should use the default resctrlfs masks (that is for the default group). > 4) Usefulness of exposing minimum unit size. > > Rather than specify unit sizes (which forces the user > to convert every time the command is executed), why not specify > in kbytes and round up? > > <resctrl name='L3' unit='KiB' cache_size='56320' > cache_unit='2816'/> > > As noted in item 1 of > https://www.redhat.com/archives/libvir-list/2017-January/msg00494.html, > "1) Convertion of kbytes (user specification) --> number of CBM bits > for host.", > the format where the size is stored is kbytes, so its awkward > to force users and OpenStack to perform the convertion themselves > (and zero benefits... nothing changes if you know the unit size). 5) Please perform necessary filesystem locking as described at Documentation/x86/intel_rdt_ui.txt in the kernel source.