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    SubjectRe: [PATCH 3/5] mm: slub allocation fairness
    On Mon, 14 May 2007, Peter Zijlstra wrote:

    > Index: linux-2.6-git/include/linux/slub_def.h
    > ===================================================================
    > --- linux-2.6-git.orig/include/linux/slub_def.h
    > +++ linux-2.6-git/include/linux/slub_def.h
    > @@ -52,6 +52,7 @@ struct kmem_cache {
    > struct kmem_cache_node *node[MAX_NUMNODES];
    > #endif
    > struct page *cpu_slab[NR_CPUS];
    > + int rank;
    > };

    Ranks as part of the kmem_cache structure? I thought this is a temporary
    thing?

    > * Lock order:
    > @@ -961,6 +962,8 @@ static struct page *allocate_slab(struct
    > if (!page)
    > return NULL;
    >
    > + s->rank = page->index;
    > +

    Argh.... Setting a cache structure field from a page struct field? What
    about concurrency?

    > @@ -1371,8 +1376,12 @@ static void *__slab_alloc(struct kmem_ca
    > gfp_t gfpflags, int node, void *addr, struct page *page)
    > {
    > void **object;
    > - int cpu = smp_processor_id();
    > + int cpu;
    > +
    > + if (page == FORCE_PAGE)
    > + goto force_new;
    >
    > + cpu = smp_processor_id();
    > if (!page)
    > goto new_slab;
    >
    > @@ -1405,6 +1414,7 @@ have_slab:
    > goto load_freelist;
    > }
    >
    > +force_new:
    > page = new_slab(s, gfpflags, node);
    > if (page) {
    > cpu = smp_processor_id();
    > @@ -1465,15 +1475,22 @@ static void __always_inline *slab_alloc(
    > struct page *page;
    > void **object;
    > unsigned long flags;
    > + int rank = slab_alloc_rank(gfpflags);
    >
    > local_irq_save(flags);
    > + if (slab_insufficient_rank(s, rank)) {
    > + page = FORCE_PAGE;
    > + goto force_alloc;
    > + }
    > +
    > page = s->cpu_slab[smp_processor_id()];
    > if (unlikely(!page || !page->lockless_freelist ||
    > - (node != -1 && page_to_nid(page) != node)))
    > + (node != -1 && page_to_nid(page) != node))) {
    >
    > +force_alloc:
    > object = __slab_alloc(s, gfpflags, node, addr, page);
    >
    > - else {
    > + } else {
    > object = page->lockless_freelist;
    > page->lockless_freelist = object[page->offset];
    > }

    This is the hot path. No modifications please.


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