On Sun, May 16, 2021 at 06:32:25PM +0800, Yanan Wang wrote:
> In implementations of ARM architecture, at most there could be a
> cpu hierarchy like "sockets/dies/clusters/cores/threads" defined.
> For example, ARM64 server chip Kunpeng 920 totally has 2 sockets,
> 2 NUMA nodes (also means cpu dies) in each socket, 6 clusters in
> each NUMA node, 4 cores in each cluster, and doesn't support SMT.
> Clusters within the same NUMA share a L3 cache and cores within
> the same cluster share a L2 cache.
>
> The cache affinity of ARM cluster has been proved to improve the
> kernel scheduling performance and a patchset has been posted, in
> which a general sched_domain for clusters was added and a cluster
> level was added in the arch-neutral cpu topology struct like below.
>
> struct cpu_topology {
> int thread_id;
> int core_id;
> int cluster_id;
> int package_id;
> int llc_id;
> cpumask_t thread_sibling;
> cpumask_t core_sibling;
> cpumask_t cluster_sibling;
> cpumask_t llc_sibling;
> }
>
> In virtuallization, exposing the cluster level topology to guest
> kernel may also improve the scheduling performance. So let's add
> the -smp, clusters=* command line support for ARM cpu, then users
> will be able to define a four-level cpu hierarchy for machines
> and it will be sockets/clusters/cores/threads.
>
> Because we only support clusters for ARM cpu currently, a new member
> "smp_clusters" is only added to the VirtMachineState structure.
>
> Signed-off-by: Yanan Wang <wangyana...@huawei.com>
> ---
> include/hw/arm/virt.h | 1 +
> qemu-options.hx | 26 +++++++++++++++-----------
> softmmu/vl.c | 3 +++
> 3 files changed, 19 insertions(+), 11 deletions(-)
>
> diff --git a/include/hw/arm/virt.h b/include/hw/arm/virt.h
> index f546dd2023..74fff9667b 100644
> --- a/include/hw/arm/virt.h
> +++ b/include/hw/arm/virt.h
> @@ -156,6 +156,7 @@ struct VirtMachineState {
> char *pciehb_nodename;
> const int *irqmap;
> int fdt_size;
> + unsigned smp_clusters;
> uint32_t clock_phandle;
> uint32_t gic_phandle;
> uint32_t msi_phandle;
> diff --git a/qemu-options.hx b/qemu-options.hx
> index bd97086c21..245eb415a6 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -184,25 +184,29 @@ SRST
> ERST
>
> DEF("smp", HAS_ARG, QEMU_OPTION_smp,
> - "-smp
> [cpus=]n[,maxcpus=cpus][,cores=cores][,threads=threads][,dies=dies][,sockets=sockets]\n"
> + "-smp
> [cpus=]n[,maxcpus=cpus][,cores=cores][,threads=threads][,clusters=clusters][,dies=dies][,sockets=sockets]\n"
> " set the number of CPUs to 'n' [default=1]\n"
> " maxcpus= maximum number of total cpus, including\n"
> " offline CPUs for hotplug, etc\n"
> - " cores= number of CPU cores on one socket (for PC, it's
> on one die)\n"
> + " cores= number of CPU cores on one socket\n"
> + " (it's on one die for PC, and on one cluster for ARM)\n"
> " threads= number of threads on one CPU core\n"
> + " clusters= number of CPU clusters on one socket (for ARM
> only)\n"
> " dies= number of CPU dies on one socket (for PC only)\n"
> " sockets= number of discrete sockets in the system\n",
> QEMU_ARCH_ALL)
> SRST
> -``-smp
> [cpus=]n[,cores=cores][,threads=threads][,dies=dies][,sockets=sockets][,maxcpus=maxcpus]``
> - Simulate an SMP system with n CPUs. On the PC target, up to 255 CPUs
> - are supported. On Sparc32 target, Linux limits the number of usable
> - CPUs to 4. For the PC target, the number of cores per die, the
> - number of threads per cores, the number of dies per packages and the
> - total number of sockets can be specified. Missing values will be
> - computed. If any on the three values is given, the total number of
> - CPUs n can be omitted. maxcpus specifies the maximum number of
> - hotpluggable CPUs.
> +``-smp
> [cpus=]n[,cores=cores][,threads=threads][,clusters=clusters][,dies=dies][,sockets=sockets][,maxcpus=maxcpus]``
> + Simulate an SMP system with n CPUs. On the PC target, up to 255
> + CPUs are supported. On the Sparc32 target, Linux limits the number
> + of usable CPUs to 4. For the PC target, the number of threads per
> + core, the number of cores per die, the number of dies per package
> + and the total number of sockets can be specified. For the ARM target,
> + the number of threads per core, the number of cores per cluster, the
> + number of clusters per socket and the total number of sockets can be
> + specified. And missing values will be computed. If any of the five
^ Why did you add this 'And'?
> + values is given, the total number of CPUs n can be omitted.
The last two sentences are not valid for Arm, which requires most of its
parameters to be given.
> Maxcpus
> + specifies the maximum number of hotpluggable CPUs.
>
> For the ARM target, at least one of cpus or maxcpus must be provided.
> Threads will default to 1 if not provided. Sockets and cores must be
> diff --git a/softmmu/vl.c b/softmmu/vl.c
> index 307944aef3..69a5c73ef7 100644
> --- a/softmmu/vl.c
> +++ b/softmmu/vl.c
> @@ -719,6 +719,9 @@ static QemuOptsList qemu_smp_opts = {
> }, {
> .name = "dies",
> .type = QEMU_OPT_NUMBER,
> + }, {
> + .name = "clusters",
> + .type = QEMU_OPT_NUMBER,
> }, {
> .name = "cores",
> .type = QEMU_OPT_NUMBER,
> --
> 2.19.1
>
Thanks,
drew
