On Fri, Nov 11, 2011 at 10:07 PM, Christoph Lameter <cl@xxxxxxxxx> wrote:
> The node field is always page_to_nid(c->page). So its rather easy to
> replace. Note that there will be additional overhead in various hot paths
> due to the need to mask a set of bits in page->flags and shift the
> result.
>
> Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
This is a nice cleanup even if we never go irqless in the slowpaths.
Is page_to_nid() really that slow?
>
> ---
> include/linux/slub_def.h | 1 -
> mm/slub.c | 15 ++++++---------
> 2 files changed, 6 insertions(+), 10 deletions(-)
>
> Index: linux-2.6/mm/slub.c
> ===================================================================
> --- linux-2.6.orig/mm/slub.c 2011-11-08 09:53:04.043865616 -0600
> +++ linux-2.6/mm/slub.c 2011-11-09 11:10:46.111334466 -0600
> @@ -1551,7 +1551,6 @@ static void *get_partial_node(struct kme
>
> if (!object) {
> c->page = page;
> - c->node = page_to_nid(page);
> stat(s, ALLOC_FROM_PARTIAL);
> object = t;
> available = page->objects - page->inuse;
> @@ -2016,7 +2015,7 @@ static void flush_all(struct kmem_cache
> static inline int node_match(struct kmem_cache_cpu *c, int node)
> {
> #ifdef CONFIG_NUMA
> - if (node != NUMA_NO_NODE && c->node != node)
> + if (node != NUMA_NO_NODE && page_to_nid(c->page) != node)
> return 0;
> #endif
> return 1;
> @@ -2105,7 +2104,6 @@ static inline void *new_slab_objects(str
> page->freelist = NULL;
>
> stat(s, ALLOC_SLAB);
> - c->node = page_to_nid(page);
> c->page = page;
> *pc = c;
> } else
> @@ -2202,7 +2200,6 @@ new_slab:
> if (c->partial) {
> c->page = c->partial;
> c->partial = c->page->next;
> - c->node = page_to_nid(c->page);
> stat(s, CPU_PARTIAL_ALLOC);
> c->freelist = NULL;
> goto redo;
> @@ -2233,7 +2230,6 @@ new_slab:
>
> c->freelist = get_freepointer(s, object);
> deactivate_slab(s, c);
> - c->node = NUMA_NO_NODE;
> local_irq_restore(flags);
> return object;
> }
> @@ -4437,9 +4433,10 @@ static ssize_t show_slab_objects(struct
> struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);
> struct page *page;
>
> - if (!c || c->node < 0)
> + if (!c || !c->page)
> continue;
>
> + node = page_to_nid(c->page);
> if (c->page) {
> if (flags & SO_TOTAL)
> x = c->page->objects;
> @@ -4449,16 +4446,16 @@ static ssize_t show_slab_objects(struct
> x = 1;
>
> total += x;
> - nodes[c->node] += x;
> + nodes[node] += x;
> }
> page = c->partial;
>
> if (page) {
> x = page->pobjects;
> total += x;
> - nodes[c->node] += x;
> + nodes[node] += x;
> }
> - per_cpu[c->node]++;
> + per_cpu[node]++;
> }
> }
>
> Index: linux-2.6/include/linux/slub_def.h
> ===================================================================
> --- linux-2.6.orig/include/linux/slub_def.h 2011-11-08 09:53:03.979865196 -0600
> +++ linux-2.6/include/linux/slub_def.h 2011-11-09 11:10:46.121334523 -0600
> @@ -45,7 +45,6 @@ struct kmem_cache_cpu {
> unsigned long tid; /* Globally unique transaction id */
> struct page *page; /* The slab from which we are allocating */
> struct page *partial; /* Partially allocated frozen slabs */
> - int node; /* The node of the page (or -1 for debug) */
> #ifdef CONFIG_SLUB_STATS
> unsigned stat[NR_SLUB_STAT_ITEMS];
> #endif
>
> --
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