Hi
> On Thu, 28 Apr 2011 23:17:15 +0900 (JST)
> KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx> wrote:
>
> > NUMA_NO_NODE and numa_node_id() are different meanings. NUMA_NO_NODE
> > is obviously recomended fallback.
> >
> > Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
> > ---
> > lib/cpumask.c | 2 +-
> > 1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/lib/cpumask.c b/lib/cpumask.c
> > index 4f6425d..af3e581 100644
> > --- a/lib/cpumask.c
> > +++ b/lib/cpumask.c
> > @@ -131,7 +131,7 @@ EXPORT_SYMBOL(zalloc_cpumask_var_node);
> > */
> > bool alloc_cpumask_var(cpumask_var_t *mask, gfp_t flags)
> > {
> > - return alloc_cpumask_var_node(mask, flags, numa_node_id());
> > + return alloc_cpumask_var_node(mask, flags, NUMA_NO_NODE);
> > }
> > EXPORT_SYMBOL(alloc_cpumask_var);
> >
>
> So effectively this will replace numa_node_id() with numa_mem_id(),
> yes? What runtime effects might this have?
If I understand correctly,
alloc_pages_node(): same effect both NUMA_NO_NODE and numa_node_id()
kmalloc_node(): not same effect NUMA_NO_NODE and numa_node_id()
because
slub.c
---------------------------------------------------
slab_alloc() {
(snip)
if (unlikely(!object || !node_match(c, node)))
// slow path
else {
// fast path
and
static inline int node_match(struct kmem_cache_cpu *c, int node)
{
#ifdef CONFIG_NUMA
if (node != NUMA_NO_NODE && c->node != node)
return 0;
#endif
return 1;
}
---------------------------------------------------
In a nutshell, numa_node_id() reduce slab cache reusing chance.
Oh, I missed slab.c code. It's using numa_mem_id(). thank you correct me!
numa_mem_id() don't have much meanings. It's ia64 HP big machine quirk.
it only affect to improve slab performance a little if users try to allocate
a memory from a cpu within memoryless node . and, 99% users never use such machine.
In a nutshell, NUMA_NO_NODE and numa_node_id() don't have a lot of difference
if users are using SLAB.
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