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    SubjectRe: [PATCH 6/6] Use one zonelist that is filtered by nodemask
    On (09/11/07 07:45), Christoph Lameter didst pronounce:
    > On Fri, 9 Nov 2007, Mel Gorman wrote:
    >
    > > struct page * fastcall
    > > __alloc_pages(gfp_t gfp_mask, unsigned int order,
    > > struct zonelist *zonelist)
    > > {
    > > + /*
    > > + * Use a temporary nodemask for __GFP_THISNODE allocations. If the
    > > + * cost of allocating on the stack or the stack usage becomes
    > > + * noticable, allocate the nodemasks per node at boot or compile time
    > > + */
    > > + if (unlikely(gfp_mask & __GFP_THISNODE)) {
    > > + nodemask_t nodemask;
    >
    > Hmmm.. This places a potentially big structure on the stack. nodemask can
    > contain up to 1024 bits which means 128 bytes. Maybe keep an array of
    > gfp_thisnode nodemasks (node_nodemask?) and use node_nodemask[nid]?

    Went back and revisited this. Allocating them at boot-time is below but
    essentially it is a silly and it makes sense to just have two zonelists
    where one of them is for __GFP_THISNODE. Implementation wise, this involves
    dropping the last patch in the set and the overall result is still a reduction
    in the number of zonelists.

    diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.24-rc2-mm1-040_use_one_zonelist/include/linux/gfp.h linux-2.6.24-rc2-mm1-045_use_static_nodemask/include/linux/gfp.h
    --- linux-2.6.24-rc2-mm1-040_use_one_zonelist/include/linux/gfp.h 2007-11-19 19:27:15.000000000 +0000
    +++ linux-2.6.24-rc2-mm1-045_use_static_nodemask/include/linux/gfp.h 2007-11-19 19:28:55.000000000 +0000
    @@ -175,7 +175,6 @@ FASTCALL(__alloc_pages(gfp_t, unsigned i
    extern struct page *
    FASTCALL(__alloc_pages_nodemask(gfp_t, unsigned int,
    struct zonelist *, nodemask_t *nodemask));
    -extern nodemask_t *nodemask_thisnode(int nid, nodemask_t *nodemask);

    static inline struct page *alloc_pages_node(int nid, gfp_t gfp_mask,
    unsigned int order)
    @@ -187,13 +186,10 @@ static inline struct page *alloc_pages_n
    if (nid < 0)
    nid = numa_node_id();

    - /* Use a temporary nodemask for __GFP_THISNODE allocations */
    if (unlikely(gfp_mask & __GFP_THISNODE)) {
    - nodemask_t nodemask;
    -
    return __alloc_pages_nodemask(gfp_mask, order,
    node_zonelist(nid),
    - nodemask_thisnode(nid, &nodemask));
    + NODE_DATA(nid)->nodemask_thisnode);
    }

    return __alloc_pages(gfp_mask, order, node_zonelist(nid));
    diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.24-rc2-mm1-040_use_one_zonelist/include/linux/mmzone.h linux-2.6.24-rc2-mm1-045_use_static_nodemask/include/linux/mmzone.h
    --- linux-2.6.24-rc2-mm1-040_use_one_zonelist/include/linux/mmzone.h 2007-11-19 19:27:15.000000000 +0000
    +++ linux-2.6.24-rc2-mm1-045_use_static_nodemask/include/linux/mmzone.h 2007-11-19 19:28:55.000000000 +0000
    @@ -519,6 +519,9 @@ typedef struct pglist_data {
    struct zone node_zones[MAX_NR_ZONES];
    struct zonelist node_zonelist;
    int nr_zones;
    +
    + /* nodemask suitable for __GFP_THISNODE */
    + nodemask_t *nodemask_thisnode;
    #ifdef CONFIG_FLAT_NODE_MEM_MAP
    struct page *node_mem_map;
    #endif
    diff -rup -X /usr/src/patchset-0.6/bin//dontdiff linux-2.6.24-rc2-mm1-040_use_one_zonelist/mm/page_alloc.c linux-2.6.24-rc2-mm1-045_use_static_nodemask/mm/page_alloc.c
    --- linux-2.6.24-rc2-mm1-040_use_one_zonelist/mm/page_alloc.c 2007-11-19 19:27:15.000000000 +0000
    +++ linux-2.6.24-rc2-mm1-045_use_static_nodemask/mm/page_alloc.c 2007-11-19 19:28:55.000000000 +0000
    @@ -1695,28 +1695,36 @@ got_pg:
    }

    /* Creates a nodemask suitable for GFP_THISNODE allocations */
    -nodemask_t *nodemask_thisnode(int nid, nodemask_t *nodemask)
    +static inline void alloc_node_nodemask_thisnode(pg_data_t *pgdat)
    {
    - nodes_clear(*nodemask);
    - node_set(nid, *nodemask);
    + nodemask_t *nodemask_thisnode;

    - return nodemask;
    + /* Only a machine with multiple nodes needs the nodemask */
    + if (!NUMA_BUILD || num_online_nodes() == 1)
    + return;
    +
    + /* Allocate the nodemask. Serious if it fails, but not world ending */
    + nodemask_thisnode = alloc_bootmem_node(pgdat, sizeof(nodemask_t));
    + if (!nodemask_thisnode) {
    + printk(KERN_WARNING
    + "thisnode nodemask allocation failed."
    + "There may be sub-optimal NUMA placement.\n");
    + return;
    + }
    +
    + /* Initialise the nodemask to only cover the current node */
    + nodes_clear(*nodemask_thisnode);
    + node_set(pgdat->node_id, *nodemask_thisnode);
    + pgdat->nodemask_thisnode = nodemask_thisnode;
    }

    struct page * fastcall
    __alloc_pages(gfp_t gfp_mask, unsigned int order,
    struct zonelist *zonelist)
    {
    - /*
    - * Use a temporary nodemask for __GFP_THISNODE allocations. If the
    - * cost of allocating on the stack or the stack usage becomes
    - * noticable, allocate the nodemasks per node at boot or compile time
    - */
    if (unlikely(gfp_mask & __GFP_THISNODE)) {
    - nodemask_t nodemask;
    -
    - return __alloc_pages_internal(gfp_mask, order,
    - zonelist, nodemask_thisnode(numa_node_id(), &nodemask));
    + return __alloc_pages_internal(gfp_mask, order, zonelist,
    + NODE_DATA(numa_node_id())->nodemask_thisnode);
    }

    return __alloc_pages_internal(gfp_mask, order, zonelist, NULL);
    @@ -3501,6 +3509,7 @@ void __meminit free_area_init_node(int n
    calculate_node_totalpages(pgdat, zones_size, zholes_size);

    alloc_node_mem_map(pgdat);
    + alloc_node_nodemask_thisnode(pgdat);

    free_area_init_core(pgdat, zones_size, zholes_size);
    }
    --
    Mel Gorman
    Part-time Phd Student Linux Technology Center
    University of Limerick IBM Dublin Software Lab
    -
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