Re: [PATCH] selftest/vm: Fix ksm selftest to run with different NUMA topologies

[Pasha Tatashin <pasha.tatashin@soleen.com>]

On Mon, Sep 13, 2021 at 8:32 AM Aneesh Kumar K.V
<aneesh.kumar@linux.ibm.com> wrote:
>

Hi Aneesh,

Thank you for this fix. My comments below:

> Platforms can have non-contiguous NUMA nodes like below

Thanks for catching this.

> +static unsigned long get_next_mem_node(unsigned long node)



NUMA should be "int" not "unsigned long", especially as it is
confusing with negative numbers used in get_first_mem_node(). Also,
numa_max_node() returns int.

> +{
> +
> +       long node_size;
> +       unsigned long i;
> +       unsigned long max_node = numa_max_node();
> +       /*
> +        * start from node and find the next memory node
> +        */
> +restart:
> +       for (i = node + 1; i <= max_node; i++) {
> +               node_size = numa_node_size(i, NULL);
> +               if (node_size > 0)
> +                       return i;
> +       }
> +       node = -1;
> +       goto restart;
> +}

I would rewrite the above without goto, and possibility of stacking in
an infinite loop. Something like this should work:

       for (i = node + 1; i <= max_node + node; i++) {
               node_size = numa_node_size(i % (max_node + 1), NULL);
               if (node_size > 0)
                       break;
       }

        return i % (max_node + 1);

> +
> +static unsigned long get_first_mem_node(void)
> +{
> +       return get_next_mem_node(-1);

Next after the last node would make more sense:

return get_next_mem_node(numa_max_node());


> +}
> +
>  static int check_ksm_numa_merge(int mapping, int prot, int timeout, bool merge_across_nodes,
>                                 size_t page_size)
>  {
>         void *numa1_map_ptr, *numa2_map_ptr;
>         struct timespec start_time;
>         int page_count = 2;
> +       unsigned long first_node;

Please use int.

>
>         if (clock_gettime(CLOCK_MONOTONIC_RAW, &start_time)) {
>                 perror("clock_gettime");
> @@ -370,7 +395,7 @@ static int check_ksm_numa_merge(int mapping, int prot, int timeout, bool merge_a
>                 perror("NUMA support not enabled");
>                 return KSFT_SKIP;
>         }
> -       if (numa_max_node() < 1) {
> +       if (numa_num_configured_nodes() <= 1) {
>                 printf("At least 2 NUMA nodes must be available\n");
>                 return KSFT_SKIP;
>         }
> @@ -378,8 +403,9 @@ static int check_ksm_numa_merge(int mapping, int prot, int timeout, bool merge_a
>                 return KSFT_FAIL;
>
>         /* allocate 2 pages in 2 different NUMA nodes and fill them with the same data */
> -       numa1_map_ptr = numa_alloc_onnode(page_size, 0);
> -       numa2_map_ptr = numa_alloc_onnode(page_size, 1);
> +       first_node = get_first_mem_node();
> +       numa1_map_ptr = numa_alloc_onnode(page_size, first_node);
> +       numa2_map_ptr = numa_alloc_onnode(page_size, get_next_mem_node(first_node));

Thanks,
Pasha