Re: [Qemu-devel] [PATCH 2/2] Add monitor command mem-nodes

[Anthony Liguori]

Wanlong Gao <address@hidden> writes:

> Add monitor command mem-nodes to show the huge mapped
> memory nodes locations.
>
> (qemu) info mem-nodes
> /proc/14132/fd/13: 00002aaaaac00000-00002aaaeac00000: node0
> /proc/14132/fd/13: 00002aaaeac00000-00002aab2ac00000: node1
> /proc/14132/fd/14: 00002aab2ac00000-00002aab2b000000: node0
> /proc/14132/fd/14: 00002aab2b000000-00002aab2b400000: node1

This creates an ABI that we don't currently support.  Memory hotplug or
a variety of things can break this mapping and then we'd have to provide
an interface to describe that the mapping was broken.

Also, it only works with hugetlbfs which is probbably not widely used
given the existance of THP.

I had hoped that we would get proper userspace interfaces for describing
memory groups but that appears to have stalled out.

Does anyone know if this is still on the table?

If we can't get a proper kernel interface, then perhaps we need to add
full libnuma support but that would really be unfortunate...

Regards,

Anthony Liguori

>
> Refer to the proposal of Eduardo and Daniel.
> http://article.gmane.org/gmane.comp.emulators.kvm.devel/93476
>
> Signed-off-by: Wanlong Gao <address@hidden>
> ---
>  monitor.c | 45 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 45 insertions(+)
>
> diff --git a/monitor.c b/monitor.c
> index eefc7f0..85c865f 100644
> --- a/monitor.c
> +++ b/monitor.c
> @@ -74,6 +74,10 @@
>  #endif
>  #include "hw/lm32/lm32_pic.h"
>  
> +#if defined(CONFIG_NUMA)
> +#include <numaif.h>
> +#endif
> +
>  //#define DEBUG
>  //#define DEBUG_COMPLETION
>  
> @@ -1759,6 +1763,38 @@ static void mem_info(Monitor *mon, const QDict *qdict)
>  }
>  #endif
>  
> +#if defined(CONFIG_NUMA)
> +static void mem_nodes(Monitor *mon, const QDict *qdict)
> +{
> +    RAMBlock *block;
> +    int prevnode, node;
> +    unsigned long long c, start, area;
> +    int fd;
> +    int pid = getpid();
> +    QTAILQ_FOREACH(block, &ram_list.blocks, next) {
> +        if (!(fd = block->fd))
> +            continue;
> +        prevnode = -1;
> +        start = 0;
> +        area = (unsigned long long)block->host;
> +        for (c = 0; c < block->length; c += TARGET_PAGE_SIZE) {
> +            if (get_mempolicy(&node, NULL, 0, c + block->host,
> +                              MPOL_F_ADDR | MPOL_F_NODE) < 0)
> +                continue;
> +            if (node == prevnode)
> +                continue;
> +            if (prevnode != -1)
> +                monitor_printf(mon, "/proc/%d/fd/%d: %016Lx-%016Lx: 
> node%d\n",
> +                               pid, fd, start + area, c + area, prevnode);
> +            prevnode = node;
> +            start = c;
> +         }
> +         monitor_printf(mon, "/proc/%d/fd/%d: %016Lx-%016Lx: node%d\n",
> +                        pid, fd, start + area, c + area, prevnode);
> +    }
> +}
> +#endif
> +
>  #if defined(TARGET_SH4)
>  
>  static void print_tlb(Monitor *mon, int idx, tlb_t *tlb)
> @@ -2567,6 +2603,15 @@ static mon_cmd_t info_cmds[] = {
>          .mhandler.cmd = mem_info,
>      },
>  #endif
> +#if defined(CONFIG_NUMA)
> +    {
> +        .name       = "mem-nodes",
> +        .args_type  = "",
> +        .params     = "",
> +        .help       = "show the huge mapped memory nodes location",
> +        .mhandler.cmd = mem_nodes,
> +    },
> +#endif
>      {
>          .name       = "mtree",
>          .args_type  = "",
> -- 
> 1.8.3.rc2.10.g0c2b1cf