On Mon, Jan 03, 2022 at 04:46:30PM +0800, Yanan Wang wrote: > ARM64 machines like Kunpeng Family Server Chips have a level > of hardware topology in which a group of CPU cores share L3 > cache tag or L2 cache. For example, Kunpeng 920 typically > has 6 or 8 clusters in each NUMA node (also represent range > of CPU die), and each cluster has 4 CPU cores. All clusters > share L3 cache data, but CPU cores in each cluster share a > local L3 tag. > > Running a guest kernel with Cluster-Aware Scheduling on the > Hosts which have physical clusters, if we can design a vCPU > topology with cluster level for guest kernel and then have > a dedicated vCPU pinning, the guest will gain scheduling > performance improvement from cache affinity of CPU cluster. > > So let's enable the support for this new parameter on ARM > virt machines. After this patch, we can define a 4-level > CPU hierarchy like: cpus=*,maxcpus=*,sockets=*,clusters=*, > cores=*,threads=*. > > Signed-off-by: Yanan Wang <wangyana...@huawei.com> > --- > hw/arm/virt.c | 1 + > qemu-options.hx | 10 ++++++++++ > 2 files changed, 11 insertions(+) > > diff --git a/hw/arm/virt.c b/hw/arm/virt.c > index 6bce595aba..f413e146d9 100644 > --- a/hw/arm/virt.c > +++ b/hw/arm/virt.c > @@ -2700,6 +2700,7 @@ static void virt_machine_class_init(ObjectClass *oc, > void *data) > hc->unplug_request = virt_machine_device_unplug_request_cb; > hc->unplug = virt_machine_device_unplug_cb; > mc->nvdimm_supported = true; > + mc->smp_props.clusters_supported = true; > mc->auto_enable_numa_with_memhp = true; > mc->auto_enable_numa_with_memdev = true; > mc->default_ram_id = "mach-virt.ram"; > diff --git a/qemu-options.hx b/qemu-options.hx > index fd1f8135fb..69ef1cdb85 100644 > --- a/qemu-options.hx > +++ b/qemu-options.hx > @@ -277,6 +277,16 @@ SRST > > -smp 16,sockets=2,dies=2,cores=2,threads=2,maxcpus=16 > > + The following sub-option defines a CPU topology hierarchy (2 sockets > + totally on the machine, 2 clusters per socket, 2 cores per cluster, > + 2 threads per core) for ARM virt machines which support sockets/clusters > + /cores/threads. Some members of the option can be omitted but their > values > + will be automatically computed: > + > + :: > + > + -smp 16,sockets=2,clusters=2,cores=2,threads=2,maxcpus=16 > + > Historically preference was given to the coarsest topology parameters > when computing missing values (ie sockets preferred over cores, which > were preferred over threads), however, this behaviour is considered > -- > 2.27.0 >
Reviewed-by: Andrew Jones <drjo...@redhat.com>
