Re: [libvirt] [PATCH v2] numa: warn if numa 'mem' option or default RAM splitting between nodes is used.

On Wed, 6 Mar 2019 18:16:08 +0000 Daniel P. Berrangé <berrange(a)redhat.com&gt; wrote: > On Wed, Mar 06, 2019 at 06:33:25PM +0100, Igor Mammedov wrote: > > Amend -numa option docs and print warnings if 'mem' option or default RAM > > splitting between nodes is used. It's intended to discourage users from using > > configuration that allows only to fake NUMA on guest side while leading > > to reduced performance of the guest due to inability to properly configure > > VM's RAM on the host. > > > > In NUMA case, it's recommended to always explicitly configure guest RAM > > using -numa node,memdev={backend-id} option. > > > > Signed-off-by: Igor Mammedov <imammedo(a)redhat.com&gt; > > --- > > numa.c | 5 +++++ > > qemu-options.hx | 12 ++++++++---- > > 2 files changed, 13 insertions(+), 4 deletions(-) > > > > diff --git a/numa.c b/numa.c > > index 3875e1e..42838f9 100644 > > --- a/numa.c > > +++ b/numa.c > > @@ -121,6 +121,8 @@ static void parse_numa_node(MachineState *ms, NumaNodeOptions *node, > > > > if (node->has_mem) { > > numa_info[nodenr].node_mem = node->mem; > > + warn_report("Parameter -numa node,mem is obsolete," > > + " use -numa node,memdev instead"); > > My comments from v1 still apply. We must not do this as long as > libvirt has no choice but to continue using this feature. It has a choice to use 'memdev' whenever creating a new VM and continue using 'mem' with exiting VMs.