Re: [Qemu-devel] [RFC PATCH v3] numa: enable sparse node numbering

[Igor Mammedov <imammedo@redhat.com>]

On Tue, 24 Jun 2014 10:40:38 -0700
Nishanth Aravamudan <nacc@linux.vnet.ibm.com> wrote:

> Sparse node numbering occurs on powerpc in practice under PowerVM. In
> order to emulate the same NUMA topology under qemu, the assumption that
> NUMA nodes are linearly ordered has to be removed. qemu actually already
> supports (inasmuch as it doesn't throw an error) sparse node numbering
> by the end-user, but the information is effectively ignored and the
> nodes are populated linearly starting at 0. This means a user's node ID
> requests are not honored in the Linux kernel, and that the topology may
> not be as requested (in terms of the CPU/memory placement).
> 
> Add a present field to NodeInfo which indicates if a given nodeid was
> present on the command-line or not. Current code relies on a memory
> value being passed for a node to indicate presence, which is
> insufficient in the presence of memoryless nodes or sparse numbering.
> Adjust the iteration of various NUMA loops to use the maximum known NUMA
> ID rather than the number of NUMA nodes.
> 
> numa.c::set_numa_nodes() has become a bit more convoluted for
> round-robin'ing the CPUs over known nodes when not specified by the
> user.
> 
> Note that architecture-specific code still possibly needs changes
> (forthcoming) for both sparse node numbering and memoryless nodes. This
> only puts in the generic infrastructure to support that.
> 
> Examples:
> 
> (1) qemu-system-x86_64 -enable-kvm -m 4096 -numa node,nodeid=3 -numa
> node,nodeid=2 -smp 16
> 
> Before:
> 
> node 0 cpus: 0 2 4 6 8 10 12 14
> node 0 size: 2048 MB
> node 1 cpus: 1 3 5 7 9 11 13 15
> node 1 size: 2048 MB
> 
> After:
> 
> node 2 cpus: 0 2 4 6 8 10 12 14                                               |
> node 2 size: 2048 MB                                                          |
> node 3 cpus: 1 3 5 7 9 11 13 15                                               |
> node 3 size: 2048 MB
> 
> (2) qemu-system-x86_64 -enable-kvm -m 4096 -numa node,nodeid=0 -numa
> node,nodeid=1 -numa node,nodeid=2 -numa node,nodeid=3 -smp 16
> 
> node 0 cpus: 0 4 8 12                                                         |
> node 0 size: 1024 MB                                                          |
> node 1 cpus: 1 5 9 13                                                         |
> node 1 size: 1024 MB                                                          |
> node 2 cpus: 2 6 10 14                                                        |
> node 2 size: 1024 MB                                                          |
> node 3 cpus: 3 7 11 15                                                        |
> node 3 size: 1024 MB
> 
> (qemu) info numa
> 4 nodes
> node 0 cpus: 0 4 8 12
> node 0 size: 1024 MB
> node 1 cpus: 1 5 9 13
> node 1 size: 1024 MB
> node 2 cpus: 2 6 10 14
> node 2 size: 1024 MB
> node 3 cpus: 3 7 11 15
> node 3 size: 1024 MB
> 
> Signed-off-by: Nishanth Aravamudan <nacc@linux.vnet.ibm.com>
> Tested-by: Hu Tao <hutao@cn.fujitsu.com>
> 
> ---
> Based off mst's for_upstream tag, which has the NodeInfo changes.
> 
> v1 -> v2:
>   Modify set_numa_nodes loop for round-robin'ing CPUs.
> 
> v2 -> v3:
>   Updated changelog to indicate problem being solved.
>   Updated memory_region_allocate_system_memory based upon feedback from
>     Hu.
>   Updated set_numa_nodes loop again to be simpler based upon feedback
>     from Hu.
>   Fixed bug with a mix of nodes with nodeid specified and without, where
>     the same nodeid would be used by the explicit specification and the
>     auto-numbering code.
> 
> diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h
> index 277230d..b90bf66 100644
> --- a/include/sysemu/sysemu.h
> +++ b/include/sysemu/sysemu.h
> @@ -145,11 +145,13 @@ extern int mem_prealloc;
>   */
>  #define MAX_CPUMASK_BITS 255
>  
> -extern int nb_numa_nodes;
> +extern int nb_numa_nodes; /* Number of NUMA nodes */
> +extern int max_numa_node; /* Highest specified NUMA node ID */
>  typedef struct node_info {
>      uint64_t node_mem;
>      DECLARE_BITMAP(node_cpu, MAX_CPUMASK_BITS);
>      struct HostMemoryBackend *node_memdev;
> +    bool present;
How about dropping 'present' and replacing array with a list
of only present nodes?
That way it will be one more step closer to converting numa
infrastructure to a set of QOM objects.


>  } NodeInfo;
>  extern NodeInfo numa_info[MAX_NODES];
>  void set_numa_nodes(void);
> diff --git a/monitor.c b/monitor.c
> index c7f8797..4721996 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -2003,7 +2003,10 @@ static void do_info_numa(Monitor *mon, const QDict *qdict)
>      CPUState *cpu;
>  
>      monitor_printf(mon, "%d nodes\n", nb_numa_nodes);
> -    for (i = 0; i < nb_numa_nodes; i++) {
> +    for (i = 0; i < max_numa_node; i++) {
> +        if (!numa_info[i].present) {
> +            continue;
> +        }
>          monitor_printf(mon, "node %d cpus:", i);
>          CPU_FOREACH(cpu) {
>              if (cpu->numa_node == i) {
> diff --git a/numa.c b/numa.c
> index e471afe..d6b86ab 100644
> --- a/numa.c
> +++ b/numa.c
> @@ -53,7 +53,10 @@ static void numa_node_parse(NumaNodeOptions *node, QemuOpts *opts, Error **errp)
>      if (node->has_nodeid) {
>          nodenr = node->nodeid;
>      } else {
> -        nodenr = nb_numa_nodes;
> +        nodenr = 0;
> +        while (numa_info[nodenr].present) {
> +            nodenr++;
> +        }
>      }
>  
>      if (nodenr >= MAX_NODES) {
> @@ -106,6 +109,10 @@ static void numa_node_parse(NumaNodeOptions *node, QemuOpts *opts, Error **errp)
>          numa_info[nodenr].node_mem = object_property_get_int(o, "size", NULL);
>          numa_info[nodenr].node_memdev = MEMORY_BACKEND(o);
>      }
> +    numa_info[nodenr].present = true;
> +    if (nodenr >= max_numa_node) {
> +        max_numa_node = nodenr + 1;
> +    }
>  }
>  
>  int numa_init_func(QemuOpts *opts, void *opaque)
> @@ -155,7 +162,7 @@ void set_numa_nodes(void)
>  {
>      if (nb_numa_nodes > 0) {
>          uint64_t numa_total;
> -        int i;
> +        int i, j = -1;
>  
>          if (nb_numa_nodes > MAX_NODES) {
>              nb_numa_nodes = MAX_NODES;
> @@ -164,27 +171,29 @@ void set_numa_nodes(void)
>          /* If no memory size if given for any node, assume the default case
>           * and distribute the available memory equally across all nodes
>           */
> -        for (i = 0; i < nb_numa_nodes; i++) {
> -            if (numa_info[i].node_mem != 0) {
> +        for (i = 0; i < max_numa_node; i++) {
> +            if (numa_info[i].present && numa_info[i].node_mem != 0) {
>                  break;
>              }
>          }
> -        if (i == nb_numa_nodes) {
> +        if (i == max_numa_node) {
>              uint64_t usedmem = 0;
>  
>              /* On Linux, the each node's border has to be 8MB aligned,
>               * the final node gets the rest.
>               */
> -            for (i = 0; i < nb_numa_nodes - 1; i++) {
> -                numa_info[i].node_mem = (ram_size / nb_numa_nodes) &
> -                                        ~((1 << 23UL) - 1);
> -                usedmem += numa_info[i].node_mem;
> +            for (i = 0; i < max_numa_node - 1; i++) {
> +                if (numa_info[i].present) {
> +                    numa_info[i].node_mem = (ram_size / nb_numa_nodes) &
> +                                            ~((1 << 23UL) - 1);
> +                    usedmem += numa_info[i].node_mem;
> +                }
>              }
>              numa_info[i].node_mem = ram_size - usedmem;
>          }
>  
>          numa_total = 0;
> -        for (i = 0; i < nb_numa_nodes; i++) {
> +        for (i = 0; i < max_numa_node; i++) {
>              numa_total += numa_info[i].node_mem;
>          }
>          if (numa_total != ram_size) {
> @@ -194,8 +203,9 @@ void set_numa_nodes(void)
>              exit(1);
>          }
>  
> -        for (i = 0; i < nb_numa_nodes; i++) {
> -            if (!bitmap_empty(numa_info[i].node_cpu, MAX_CPUMASK_BITS)) {
> +        for (i = 0; i < max_numa_node; i++) {
> +            if (numa_info[i].present &&
> +                !bitmap_empty(numa_info[i].node_cpu, MAX_CPUMASK_BITS)) {
>                  break;
>              }
>          }
> @@ -203,9 +213,12 @@ void set_numa_nodes(void)
>           * must cope with this anyway, because there are BIOSes out there in
>           * real machines which also use this scheme.
>           */
> -        if (i == nb_numa_nodes) {
> +        if (i == max_numa_node) {
>              for (i = 0; i < max_cpus; i++) {
> -                set_bit(i, numa_info[i % nb_numa_nodes].node_cpu);
> +                do {
> +                    j = (j + 1) % max_numa_node;
> +                } while (!numa_info[j].present);
> +                set_bit(i, numa_info[j].node_cpu);
>              }
>          }
>      }
> @@ -217,8 +230,9 @@ void set_numa_modes(void)
>      int i;
>  
>      CPU_FOREACH(cpu) {
> -        for (i = 0; i < nb_numa_nodes; i++) {
> -            if (test_bit(cpu->cpu_index, numa_info[i].node_cpu)) {
> +        for (i = 0; i < max_numa_node; i++) {
> +            if (numa_info[i].present &&
> +                test_bit(cpu->cpu_index, numa_info[i].node_cpu)) {
>                  cpu->numa_node = i;
>              }
>          }
> @@ -266,10 +280,13 @@ void memory_region_allocate_system_memory(MemoryRegion *mr, Object *owner,
>      }
>  
>      memory_region_init(mr, owner, name, ram_size);
> -    for (i = 0; i < MAX_NODES; i++) {
> +    for (i = 0; i < max_numa_node; i++) {
>          Error *local_err = NULL;
>          uint64_t size = numa_info[i].node_mem;
>          HostMemoryBackend *backend = numa_info[i].node_memdev;
> +        if (!numa_info[i].present) {
> +            continue;
> +        }
>          if (!backend) {
>              continue;
>          }
> diff --git a/vl.c b/vl.c
> index 54b4627..e1a6ab8 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -195,6 +195,7 @@ static QTAILQ_HEAD(, FWBootEntry) fw_boot_order =
>      QTAILQ_HEAD_INITIALIZER(fw_boot_order);
>  
>  int nb_numa_nodes;
> +int max_numa_node;
>  NodeInfo numa_info[MAX_NODES];
>  
>  uint8_t qemu_uuid[16];
> @@ -2967,10 +2968,12 @@ int main(int argc, char **argv, char **envp)
>  
>      for (i = 0; i < MAX_NODES; i++) {
>          numa_info[i].node_mem = 0;
> +        numa_info[i].present = false;
>          bitmap_zero(numa_info[i].node_cpu, MAX_CPUMASK_BITS);
>      }
>  
>      nb_numa_nodes = 0;
> +    max_numa_node = -1;
>      nb_nics = 0;
>  
>      bdrv_init_with_whitelist();
> 
>