From d55c316f910edcffbda6159053dfd59c7af02042 Mon Sep 17 00:00:00 2001 From: Yanan Wang Date: Fri, 7 Jan 2022 16:32:27 +0800 Subject: [PATCH] hw/arm/virt: Support CPU cluster on ARM virt machine 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 Reviewed-by: Andrew Jones Message-id: 20220107083232.16256-2-wangyanan55@huawei.com Signed-off-by: Peter Maydell --- 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 84c2444fff..688d873690 100644 --- a/hw/arm/virt.c +++ b/hw/arm/virt.c @@ -2718,6 +2718,7 @@ 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 ec90505d84..ba3ae6a42a 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