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

[Marcelo Tosatti]

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)".

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).


Thanks!