Re: [PATCH 4/4] NUMA: realize NUMA memory pinning

Marcelo Tosatti
2010-08-23T19:02:59Z

On Wed, Aug 11, 2010 at 03:52:18PM +0200, Andre Przywara wrote:
> According to the user-provided assignment bind the respective part
> of the guest's memory to the given host node. This uses Linux'
> mbind syscall (which is wrapped only in libnuma) to realize the
> pinning right after the allocation.
> Failures are not fatal, but produce a warning.
>
> Signed-off-by: Andre Przywara <andre.przywara@amd.com>
> ---
> hw/pc.c | 58 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 files changed, 58 insertions(+), 0 deletions(-)
>
> diff --git a/hw/pc.c b/hw/pc.c
> index 1b24409..dbfc082 100644
> --- a/hw/pc.c
> +++ b/hw/pc.c
> @@ -42,6 +42,15 @@
> #include "device-assignment.h"
> #include "kvm.h"
>
> +#ifdef CONFIG_NUMA
> +#include <numa.h>
> +#include <numaif.h>
> +#ifndef MPOL_F_RELATIVE_NODES
> + #define MPOL_F_RELATIVE_NODES (1 << 14)
> + #define MPOL_F_STATIC_NODES (1 << 15)
> +#endif
> +#endif
> +
> /* output Bochs bios info messages */
> //#define DEBUG_BIOS
>
> @@ -882,6 +891,53 @@ void pc_cpus_init(const char *cpu_model)
> }
> }
>
> +static void bind_numa(ram_addr_t ram_addr)
> +{
> +#ifdef CONFIG_NUMA
> + int i;
> + char* ram_ptr;
> + ram_addr_t len, ram_offset;
> + int bind_mode;
> +
> + ram_ptr = qemu_get_ram_ptr(ram_addr);
> +
> + ram_offset = 0;
> + for (i = 0; i < nb_numa_nodes; i++) {
> + len = numa_info[i].guest_mem;
> + if (numa_info[i].flags != 0) {
> + switch (numa_info[i].flags & NODE_HOST_POLICY_MASK) {
> + case NODE_HOST_BIND:
> + bind_mode = MPOL_BIND;
> + break;
> + case NODE_HOST_INTERLEAVE:
> + bind_mode = MPOL_INTERLEAVE;
> + break;
> + case NODE_HOST_PREFERRED:
> + bind_mode = MPOL_PREFERRED;
> + break;
> + default:
> + bind_mode = MPOL_DEFAULT;
> + break;
> + }
> + bind_mode |= (numa_info[i].flags & NODE_HOST_RELATIVE) ?
> + MPOL_F_RELATIVE_NODES : MPOL_F_STATIC_NODES;
> +
> + /* This is a workaround for a long standing bug in Linux'
> + * mbind implementation, which cuts off the last specified
> + * node. To stay compatible should this bug be fixed, we
> + * specify one more node and zero this one out.
> + */
> + clear_bit(numa_num_configured_nodes() + 1, numa_info[i].host_mem);
> + if (mbind(ram_ptr + ram_offset, len, bind_mode,
> + numa_info[i].host_mem, numa_num_configured_nodes() + 1, 0))
> + perror("mbind");
> + }
> + ram_offset += len;
> + }
> +#endif

Why is it not possible (or perhaps not desired) to change the binding
after the guest is started?

Sounds unflexible.