2014-12-10 16:31:40

by Christoph Lameter (Ampere)

Subject: [PATCH 4/7] slub: Avoid using the page struct address in allocation fastpath

We can use virt_to_page there and only invoke the costly function if
actually a node is specified and we have to check the NUMA locality.

Increases the cost of allocating on a specific NUMA node but then that
was never cheap since we may have to dump our caches and retrieve memory
from the correct node.

Signed-off-by: Christoph Lameter <[email protected]>

Index: linux/mm/slub.c
===================================================================
--- linux.orig/mm/slub.c 2014-12-09 12:27:49.414686959 -0600
+++ linux/mm/slub.c 2014-12-09 12:27:49.414686959 -0600
@@ -2097,6 +2097,15 @@ static inline int node_match(struct page
return 1;
}

+static inline int node_match_ptr(void *p, int node)
+{
+#ifdef CONFIG_NUMA
+ if (!p || (node != NUMA_NO_NODE && page_to_nid(virt_to_page(p)) != node))
+ return 0;
+#endif
+ return 1;
+}
+
#ifdef CONFIG_SLUB_DEBUG
static int count_free(struct page *page)
{
@@ -2410,7 +2419,7 @@ redo:

object = c->freelist;
page = c->page;
- if (unlikely(!object || !node_match(page, node))) {
+ if (unlikely(!object || !node_match_ptr(object, node))) {
object = __slab_alloc(s, gfpflags, node, addr, c);
stat(s, ALLOC_SLOWPATH);
} else {

2014-12-10 16:56:36

by Pekka Enberg

Subject: Re: [PATCH 4/7] slub: Avoid using the page struct address in allocation fastpath

On Wed, Dec 10, 2014 at 6:30 PM, Christoph Lameter <[email protected]> wrote:
> We can use virt_to_page there and only invoke the costly function if
> actually a node is specified and we have to check the NUMA locality.
>
> Increases the cost of allocating on a specific NUMA node but then that
> was never cheap since we may have to dump our caches and retrieve memory
> from the correct node.
>
> Signed-off-by: Christoph Lameter <[email protected]>
>
> Index: linux/mm/slub.c
> ===================================================================
> --- linux.orig/mm/slub.c 2014-12-09 12:27:49.414686959 -0600
> +++ linux/mm/slub.c 2014-12-09 12:27:49.414686959 -0600
> @@ -2097,6 +2097,15 @@ static inline int node_match(struct page
> return 1;
> }
>
> +static inline int node_match_ptr(void *p, int node)
> +{
> +#ifdef CONFIG_NUMA
> + if (!p || (node != NUMA_NO_NODE && page_to_nid(virt_to_page(p)) != node))

You already test that object != NULL before calling node_match_ptr().

> + return 0;
> +#endif
> + return 1;
> +}
> +
> #ifdef CONFIG_SLUB_DEBUG
> static int count_free(struct page *page)
> {
> @@ -2410,7 +2419,7 @@ redo:
>
> object = c->freelist;
> page = c->page;
> - if (unlikely(!object || !node_match(page, node))) {
> + if (unlikely(!object || !node_match_ptr(object, node))) {
> object = __slab_alloc(s, gfpflags, node, addr, c);
> stat(s, ALLOC_SLOWPATH);
> } else {
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to [email protected]. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"[email protected]"> [email protected] </a>