Re: [RFC PATCH] powerpc/numa: initialize distance lookup table from drconf path

Anton Blanchard
2015-06-23T01:16:59Z

Hi Nikunj,

> From: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
>
> powerpc/numa: initialize distance lookup table from drconf path
>
> In some situations, a NUMA guest that supports
> ibm,dynamic-memory-reconfiguration node will end up having flat NUMA
> distances between nodes. This is because of two problems in the
> current code.

Thanks for the patch. Have we tested that this doesn't regress the
non dynamic representation?

Regards,
Anton

> 1) Different representations of associativity lists.
>
> There is an assumption about the associativity list in
> initialize_distance_lookup_table(). Associativity list has two
> forms:
>
> a) [cpu,memory]@x/ibm,associativity has following
> format:
> <N> <N integers>
>
> b)
> ibm,dynamic-reconfiguration-memory/ibm,associativity-lookup-arrays
>
> <M> <N> <M associativity lists each having N integers>
> M = the number of associativity lists
> N = the number of entries per associativity list
>
> Fix initialize_distance_lookup_table() so that it does not assume
> "case a". And update the caller to skip the length field before
> sending the associativity list.
>
> 2) Distance table not getting updated from drconf path.
>
> Node distance table will not get initialized in certain cases as
> ibm,dynamic-reconfiguration-memory path does not initialize the
> lookup table.
>
> Call initialize_distance_lookup_table() from drconf path with
> appropriate associativity list.
>
> Reported-by: Bharata B Rao <bharata@linux.vnet.ibm.com>
> Signed-off-by: Nikunj A Dadhania <nikunj@linux.vnet.ibm.com>
> ---
> arch/powerpc/mm/numa.c | 16 +++++++++++++---
> 1 file changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/arch/powerpc/mm/numa.c b/arch/powerpc/mm/numa.c
> index 5e80621..8b9502a 100644
> --- a/arch/powerpc/mm/numa.c
> +++ b/arch/powerpc/mm/numa.c
> @@ -225,7 +225,7 @@ static void initialize_distance_lookup_table(int
> nid, for (i = 0; i < distance_ref_points_depth; i++) {
> const __be32 *entry;
>
> - entry =
> &associativity[be32_to_cpu(distance_ref_points[i])];
> + entry =
> &associativity[be32_to_cpu(distance_ref_points[i]) - 1];
> distance_lookup_table[nid][i] = of_read_number(entry, 1); }
> }
> @@ -248,8 +248,12 @@ static int associativity_to_nid(const __be32
> *associativity) nid = -1;
>
> if (nid > 0 &&
> - of_read_number(associativity, 1) >=
> distance_ref_points_depth)
> - initialize_distance_lookup_table(nid, associativity);
> + of_read_number(associativity, 1) >=
> distance_ref_points_depth) {
> + /*
> + * Skip the length field and send start of
> associativity array
> + */
> + initialize_distance_lookup_table(nid, associativity
> + 1);
> + }
>
> out:
> return nid;
> @@ -507,6 +511,12 @@ static int of_drconf_to_nid_single(struct
> of_drconf_cell *drmem,
> if (nid == 0xffff || nid >= MAX_NUMNODES)
> nid = default_nid;
> +
> + if (nid > 0) {
> + index = drmem->aa_index * aa->array_sz;
> + initialize_distance_lookup_table(nid,
> +
> &aa->arrays[index]);
> + }
> }
>
> return nid;

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