Thanks Michal... It seems to work ok now. (My bad that I forgot about Martin's patch for memnode related binding) Thanks! Vinod -----Original Message----- From: Michal Privoznik [mailto:mprivozn@xxxxxxxxxx] Sent: Friday, September 12, 2014 12:40 AM To: Vinod, Chegu Cc: libvir-list@xxxxxxxxxx; Eduardo Habkost (ehabkost@xxxxxxxxxx); Martin Kletzander Subject: Re: Question : Configuring a VM with backing 1G huge pages across 2 NUMA nodes [CCing Martin Kletzander] On 12.09.2014 08:25, Vinod, Chegu wrote: > Hi Michal, > > 'have a kernel+qemu+libvirt setup with all recent upstream bits on a > given host & was trying to configure a VM with backing 1G huge > pages...spanning 2 NUMA nodes. > > The host had 3 1G huge pages on each of the 2 NUMA nodes : > > # cat > /sys/devices/system/node/node0/hugepages/hugepages-1048576kB/nr_hugepa > ges > > 3 > > # cat > /sys/devices/system/node/node1/hugepages/hugepages-1048576kB/nr_hugepa > ges > > 3 > > And I had the following in the /etc/fstab > > hugetlbfs /hugepages_1G hugetlbfs pagesize=1GB 0 0 > > I added the following entries in the xml file for the 4G/4vcpu VM > > <memoryBacking> > > <hugepages> > > <page size='1048576' unit='KiB' nodeset='0'/> > > <page size='1048576' unit='KiB' nodeset='1'/> > > </hugepages> > > </memoryBacking> > > <vcpu placement='static'>4</vcpu> > > <cputune> > > <vcpupin vcpu='0' cpuset='0'/> > > <vcpupin vcpu='1' cpuset='1'/> > > <vcpupin vcpu='2' cpuset='8'/> > > <vcpupin vcpu='3' cpuset='9'/> > > </cputune> > > .... > > <numatune> > > <memory node="strict" nodeset="0-1"/> [This is a copy-paste error, right? It should have been s/node/mode/] This is incomplete. This basically says nothing more than: All the guest numa nodes must be placed on host numa nodes 0-1. And the qemu command line that libvirt came up with satisfied the constrain. You may wan to pin guest numa nodes to host numa nodes like this: A) use <memory mode="interleave" placement="static" nodeset="0-1"/> I haven't tested myself, but IIRC correctly, this should start placing guest numa nodes sequentially over host numa nodes 0-1. So You'll end up with: host0: guest0, guest2 host1: guest1, guest3 b) use the manual guest <-> host pinning: <numatune> <memory mode='strict' nodeset='0-1'/> <memnode cellid='0' mode='strict' nodeset='0'/> <memnode cellid='1' mode='strict' nodeset='0'/> <memnode cellid='2' mode='strict' nodeset='1'/> <memnode cellid='3' mode='strict' nodeset='1'/> </numatune> This will tie guest0 and guest1 onto host0, and guest2 and guets3 onto host1. I must admit this is not the bit I've implemented, so I don't know all the details. Therefore I'm CCing Martin Kletzander, who's done the major piece of work in this field. > > </numatune> > > .... > > <cpu> > > <numa> > > <cell id='0' cpus='0-1' memory='2097152'/> > > <cell id='1' cpus='2-3' memory='2097152'/> > > </numa> > > </cpu> > > The resulting qemu command looked like this : > > /usr/local/bin/qemu-system-x86_64 -name vm1 -S -machine > pc-i440fx-2.2,accel=kvm,usb=off \ > > -m 4096 -realtime mlock=off -smp 4,sockets=4,cores=1,threads=1 \ > > -object > memory-backend-file,prealloc=yes,mem-path=/hugepages_1G/libvirt/qemu,size=2048M,id=ram-node0,host-nodes=0-1,policy=bind > -numa node,nodeid=0,cpus=0-1,memdev=ram-node0 \ > > -object > memory-backend-file,prealloc=yes,mem-path=/hugepages_1G/libvirt/qemu,size=2048M,id=ram-node1,host-nodes=0-1,policy=bind > -numa node,nodeid=1,cpus=2-3,memdev=ram-node1 \ > > .... > > There were 3 1G pages available on each NUMA node on the host as shown > above... and I noticed that the VM got backed by 3 1G pages from node0 > and 1 1G page from node1. > > #cat > /sys/devices/system/node/node0/hugepages/hugepages-1048576kB/free_hugepages > > 0 > > # cat > /sys/devices/system/node/node1/hugepages/hugepages-1048576kB/free_hugepages > > 2 > > Not sure if this was expected behavior given the options I specified in > the xml file ? If yes...Is there some additional option to specify (in the > XML file) such that only a given number of 1Gig huge pages per node are > picked to back the VM (i.e. in the above case just 2 1G from each node) ? > > Thanks! > > Vinod > Hopefully, my answer is sufficient, Martin? Michal -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list