Re: [PATCH 1/2] mm: Replace nr_node_ids for loop with for_each_node in list lru

[Raghavendra K T]

On 09/14/2015 05:34 PM, Vladimir Davydov wrote:
> On Mon, Sep 14, 2015 at 05:09:31PM +0530, Raghavendra K T wrote:
> > On 09/14/2015 02:30 PM, Vladimir Davydov wrote:
> > > On Wed, Sep 09, 2015 at 12:01:46AM +0530, Raghavendra K T wrote:
> > > > The functions used in the patch are in slowpath, which gets called
> > > > whenever alloc_super is called during mounts.
> > > >
> > > > Though this should not make difference for the architectures with
> > > > sequential numa node ids, for the powerpc which can potentially have
> > > > sparse node ids (for e.g., 4 node system having numa ids, 0,1,16,17
> > > > is common), this patch saves some unnecessary allocations for
> > > > non existing numa nodes.
> > > >
> > > > Even without that saving, perhaps patch makes code more readable.
> > >
> > > Do I understand correctly that node 0 must always be in
> > > node_possible_map? I ask, because we currently test
> > > lru->node[0].memcg_lrus to determine if the list is memcg aware.
> >
> > Yes, node 0 is always there. So it should not be a problem.
>
> I think it should be mentioned in the comment to list_lru_memcg_aware
> then.

Something like this: ?
static inline bool list_lru_memcg_aware(struct list_lru *lru)
{
        /*
         * This needs node 0 to be always present, even
         * in the systems supporting sparse numa ids.
         */
        return !!lru->node[0].memcg_lrus;
}


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