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SubjectRe: [PATCH][RFC] Discontigmem support for the x440
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Hey Andy - Thanks. Martin had said that you had thought it was wrong, so I
had been looking it over this morning and realized my error :-) Hadn't worked
up a solution just yet, though... so I'm glad to some code with your comment.
I'll review your changes, and if it works I'll add it to my patch. :-) I
really appreciate your feedback!

Thanks,
Pat

>
> --=-VhECMrXvMAbfEiHvGxl0
> Content-Type: text/plain
> Content-Transfer-Encoding: 7bit
>
> Pat,
>
> Whilst looking at the Summit NUMA support I believe I have found a bug
> in the memory hole handling. Specifically, there appears to be a type
> mismatch between get_zholes_size() returning a single long and
> free_area_init_core() requiring a log array. What I cannot adequately
> explain is why this does not lead to a panic during boot.
>
> Attached is a patch against 2.5.59-mjb6 which I believe should correct
> this. It has been tested in isolation and compile tested, but as I
> don't have access to a test machine I cannot be sure it works. I
> believe some investigation is needed to understand why this bug does not
> prevent booting, or lead to a large disparity in the zone free page
> counts, perhaps the e820 map is helping here.
>
> [gory details for the interested]
> Under NUMA support constructing the memory map we call
> free_area_init_node() to initilialise the pglist_data and allocate the
> memory map structures. As part of this we supply a per node, per memory
> zone page count and a per node, per memory zone missing page count.
> These are used in free_area_init_core() to determine the true number of
> pages per node, per zone. In the existing summit code we parse the SRAT
> in order to locate and size the inter-chunk gaps, on a per node basis.
> Later this is queried via get_zholes_size() from zone_init_sizes().
> Unfortuantly, get_zholes_size is returning a single long representing
> the per node total holes, whilst zone_init_sizes() requires an array of
> longs one per zone (long[MAX_NR_ZONES]). In the zero holes case this
> will be safe as if there are zero pages of hole then we pass an
> apparently null pointer to get_zholes_size which is interpreted as
> having no holes. If the presence of any such holes a low-memory
> reference would be passed potentially leading to an oops.
>
> The attached patch modifies the memory chunk hole scan such that each
> hole is allocated to one or more zones using the calculated zone
> boundries, converting zholes_size[] from a per node count to a per node,
> per zone count in a similar form to the associated zones[] array.
>
> Cheers.
>
> -apw
>
>
> --=-VhECMrXvMAbfEiHvGxl0
> Content-Disposition: attachment; filename=patch.mjb6-zholes
> Content-Transfer-Encoding: quoted-printable
> Content-Type: text/x-patch; name=patch.mjb6-zholes; charset=UTF-8
>
> diff -X /home/apw/bin/makediff.excl -rupN linux-2.5.59-mjb6/arch/i386/kerne
> =
> l/srat.c linux-2.5.59-mjb6-zholes/arch/i386/kernel/srat.c
> --- linux-2.5.59-mjb6/arch/i386/kernel/srat.c 2003-02-12 11:28:54.000
> 000000=
> +0000
> +++ linux-2.5.59-mjb6-zholes/arch/i386/kernel/srat.c 2003-02-13 13:1
> 7:08.00=
> 0000000 +0000
> @@ -50,7 +50,8 @@ static u8 pxm_bitmap[PXM_BITMAP_LEN]; /*
> struct node_memory_chunk_s node_memory_chunk[MAXCLUMPS];
> =20
> static int num_memory_chunks; /* total number of memory chunk
> s */
> -static unsigned long zholes_size[MAX_NUMNODES];
> +static int zholes_size_init;
> +static unsigned long zholes_size[MAX_NUMNODES * MAX_NR_ZONES];
> =20
> unsigned long node_start_pfn[MAX_NUMNODES];
> unsigned long node_end_pfn[MAX_NUMNODES];
> @@ -151,6 +152,49 @@ static void __init parse_memory_affinity
> "enabled and removable" : "enabled" ) );
> }
> =20
> +#if MAX_NR_ZONES !=3D 3
> +#error "MAX_NR_ZONES !=3D 3, chunk_to_zone requires review"
> +#endif
> +/* Take a chunk of pages from page frame cstart to cend and count the numb
> =
> er
> + * of pages in each zone, returned via zones[].
> + */
> +static __init void chunk_to_zones(unsigned long cstart, unsigned long cend
> =
> ,=20
> + unsigned long *zones)
> +{
> + unsigned long max_dma;
> + extern unsigned long max_low_pfn;
> +
> + int z;
> + unsigned long rend;
> +
> + /* FIXME: MAX_DMA_ADDRESS and max_low_pfn are trying to provide
> + * similarly scoped information and should be handled in a consistant
> + * manner.
> + */
> + max_dma =3D virt_to_phys((char *)MAX_DMA_ADDRESS) >> PAGE_SHIFT;
> +
> + /* Split the hole into the zones in which it falls. Repeatedly
> + * take the segment in which the remaining hole starts, round it
> + * to the end of that zone.
> + */
> + memset(zones, 0, MAX_NR_ZONES * sizeof(long));
> + while (cstart < cend) {
> + if (cstart < max_dma) {
> + z =3D ZONE_DMA;
> + rend =3D (cend < max_dma)? cend : max_dma;
> +
> + } else if (cstart < max_low_pfn) {
> + z =3D ZONE_NORMAL;
> + rend =3D (cend < max_low_pfn)? cend : max_low_pfn;
> +
> + } else {
> + z =3D ZONE_HIGHMEM;
> + rend =3D cend;
> + }
> + zones[z] +=3D rend - cstart;
> + cstart =3D rend;
> + }
> +}
> =20
> /* Parse the ACPI Static Resource Affinity Table */
> static int __init acpi20_parse_srat(struct acpi_table_srat *sratp)
> @@ -242,10 +286,6 @@ static int __init acpi20_parse_srat(stru
> } else { /* We've found another chunk of memory
> for the node */
> if (node_start_pfn[nid] < node_memory_c
> hunk[j].start_pfn) {
> printk("found a another chunk o
> n nid %d, chunk %d\n", nid, j);
> -
> - zholes_size[nid] =3D zholes_siz
> e[nid] +
> - (node_memory_chunk[j].s
> tart_pfn
> - - node_end_pfn[nid]);
> node_end_pfn[nid] =3D node_memo
> ry_chunk[j].end_pfn;
> }
> }
> @@ -396,10 +436,53 @@ printk("Begin table scan....\n");
> wbinvd();
> }
> =20
> -unsigned long __init get_zholes_size(int nid)
> +/* For each node run the memory list to determine whether there are
> + * any memory holes. For each hole determine which ZONE they fall
> + * into.
> + *
> + * NOTE#1: this requires knowledge of the zone boundries and so
> + * _cannot_ be performed before those are calculated in setup_memory.
> + *=20
> + * NOTE#2: we rely on the fact that the memory chunks are ordered by
> + * start pfn number during setup.
> + */
> +static void __init get_zholes_init(void)
> {
> + int nid;
> + int c;
> + int first;
> + unsigned long end =3D 0;
> +
> + for (nid =3D 0; nid < numnodes; nid++) {
> + first =3D 1;
> + for (c =3D 0; c < num_memory_chunks; c++){
> + if (node_memory_chunk[c].nid =3D=3D nid) {
> + if (first) {
> + end =3D node_memory_chunk[c].end_pfn;
> + first =3D 0;
> +
> + } else {
> + /* Record any gap between this chunk
> + * and the previous chunk on this node
> + * against the zones it spans.
> + */
> + chunk_to_zones(end,
> + node_memory_chunk[c].start_pfn,
> + &zholes_size[nid * MAX_NR_ZONES
> ]);
> + }
> + }
> + }
> + }
> +}
> +
> +unsigned long * __init get_zholes_size(int nid)
> +{
> + if (!zholes_size_init) {
> + zholes_size_init++;
> + get_zholes_init();
> + }
> if((nid >=3D numnodes) | (nid >=3D MAX_NUMNODES))
> printk("%s: nid =3D %d is invalid. numnodes =3D %d",
> __FUNCTION__, nid, numnodes);
> - return zholes_size[nid];
> + return &zholes_size[nid * MAX_NR_ZONES];
> }
> diff -X /home/apw/bin/makediff.excl -rupN linux-2.5.59-mjb6/arch/i386/mm/di
> =
> scontig.c linux-2.5.59-mjb6-zholes/arch/i386/mm/discontig.c
> --- linux-2.5.59-mjb6/arch/i386/mm/discontig.c 2003-02-12 11:28:54.000
> 00000=
> 0 +0000
> +++ linux-2.5.59-mjb6-zholes/arch/i386/mm/discontig.c 2003-02-13 13:0
> 3:34.0=
> 00000000 +0000
> @@ -290,7 +290,7 @@ void __init zone_sizes_init(void)
> =20
> for (nid =3D 0; nid < numnodes; nid++) {
> unsigned long zones_size[MAX_NR_ZONES] =3D {0, 0, 0};
> - unsigned long zholes_size;
> + unsigned long *zholes_size;
> unsigned int max_dma;
> =20
> unsigned long low =3D max_low_pfn;
> @@ -331,7 +331,7 @@ void __init zone_sizes_init(void)
> lmem_map &=3D PAGE_MASK;
> free_area_init_node(nid, NODE_DATA(nid),=20
> (struct page *)lmem_map, zones_size,=20
> - start, (unsigned long *)zholes_size);
> + start, zholes_size);
> }
> }
> return;
> diff -X /home/apw/bin/makediff.excl -rupN linux-2.5.59-mjb6/include/asm-i38
> =
> 6/srat.h linux-2.5.59-mjb6-zholes/include/asm-i386/srat.h
> --- linux-2.5.59-mjb6/include/asm-i386/srat.h 2003-02-12 11:28:55.000
> 000000=
> +0000
> +++ linux-2.5.59-mjb6-zholes/include/asm-i386/srat.h 2003-02-13 11:0
> 2:43.00=
> 0000000 +0000
> @@ -34,7 +34,7 @@
> #define MAXCLUMPS (MAX_CLUMPS_PER_NODE * MAX_NUMNODES)
> extern int pfn_to_nid(unsigned long);
> extern void get_memcfg_from_srat(void);
> -extern unsigned long get_zholes_size(int);
> +extern unsigned long *get_zholes_size(int);
> #define get_memcfg_numa() get_memcfg_from_srat()
> =20
> /*
>
> --=-VhECMrXvMAbfEiHvGxl0--
>

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