Re: [libvirt] [PATCH RFC v2] qemu: Support numad

On 2012年03月07日 21:48, Daniel P. Berrange wrote: > On Wed, Mar 07, 2012 at 09:55:16PM +0800, Osier Yang wrote: >> numad is an user-level daemon that monitors NUMA topology and >> processes resource consumption to facilitate good NUMA resource >> alignment of applications/virtual machines to improve performance >> and minimize cost of remote memory latencies. It provides a >> pre-placement advisory interface, so significant processes can >> be pre-bound to nodes with sufficient available resources. >> >> More details: http://fedoraproject.org/wiki/Features/numad >> >> "numad -w ncpus:memory_amount" is the advisory interface numad >> provides currently. >> >> This patch add the support by introducing a bool XML element: >> <numatune> >> <autonuma/> >> </numatune> >> >> If it's specified, the number of vcpus and the current memory >> amount specified in domain XML will be used for numad command >> line (numad uses MB for memory amount): >> numad -w $num_of_vcpus:$current_memory_amount / 1024 >> >> The advisory nodeset returned from numad will be used to set >> domain process CPU affinity then. (e.g. qemuProcessInitCpuAffinity). >> >> If the user specifies both CPU affinity policy (e.g. >> (<vcpu cpuset="1-10,^7,^8">4</vcpu>) and XML indicating to use >> numad for the advisory nodeset, the specified CPU affinity will be >> ignored. > > I'm not sure that's a good idea. When we do dynamic generation > of parts of libvirt XML, we tend to report in the XML what was > generated, and if 2 parts contradict each other we shouldn't > silently ignore it. Agreed, v1 overrides the cpuset="1-10,^6", but I thought it could be confused for user to see things are different after domain is started. > > eg, with VNC with autoport=yes we then report the generated > port number. > > Similarly with<cpu> mode=host, we then report what the host > CPU features were. > > So, if we want to auto-set placement for a guest we should > likely do this via the<vcpu> element > > eg, Current mode where placement is completely static > > - Input XML: > > <vcpu placement="static" cpuset="1-10" /> > > - Output XML: > > <vcpu placement="static" cpuset="1-10" /> > > Or where we want to use numad: > > - Input XML: > > <vcpu placement="auto"/> > > - Output XML: > > <vcpu placement="auto" cpuset="1-10" /> > I must admit this is much better. :-) > > The current numad functionality you propose only sets the initial guest > placement. Are we likely to have a mode in the future where numad will > be called to update the placement periodically for existing guests ? Very possiable, now numad just provides the advisory interface, in future I guess it could manage the placement dynamically. > If so, then "placement" would need to have more enum values. > I will post a v3 tomorrow. Regards, Osier