Re: [PATCH 2/3] mm/slub: wrap cpu_slab->partial in CONFIG_SLUB_CPU_PARTIAL

From: Matthew Wilcox
Date: Sun Apr 30 2017 - 22:41:18 EST


On Sun, Apr 30, 2017 at 07:31:51PM +0800, Wei Yang wrote:
> @@ -2302,7 +2302,11 @@ static bool has_cpu_slab(int cpu, void *info)
> struct kmem_cache *s = info;
> struct kmem_cache_cpu *c = per_cpu_ptr(s->cpu_slab, cpu);
>
> - return c->page || c->partial;
> + return c->page
> +#ifdef CONFIG_SLUB_CPU_PARTIAL
> + || c->partial
> +#endif
> + ;
> }

No. No way. This is disgusting.

The right way to do this is to create an accessor like this:

#ifdef CONFIG_SLUB_CPU_PARTIAL
#define slub_cpu_partial(c) ((c)->partial)
#else
#define slub_cpu_partial(c) 0
#endif

And then the above becomes:

- return c->page || c->partial;
+ return c->page || slub_cpu_partial(c);

All the other ifdefs go away, apart from these two:

> @@ -4980,6 +4990,7 @@ static ssize_t objects_partial_show(struct kmem_cache *s, char *buf)
> }
> SLAB_ATTR_RO(objects_partial);
>
> +#ifdef CONFIG_SLUB_CPU_PARTIAL
> static ssize_t slabs_cpu_partial_show(struct kmem_cache *s, char *buf)
> {
> int objects = 0;
> @@ -5010,6 +5021,7 @@ static ssize_t slabs_cpu_partial_show(struct kmem_cache *s, char *buf)
> return len + sprintf(buf + len, "\n");
> }
> SLAB_ATTR_RO(slabs_cpu_partial);
> +#endif
>
> static ssize_t reclaim_account_show(struct kmem_cache *s, char *buf)
> {
> @@ -5364,7 +5376,9 @@ static struct attribute *slab_attrs[] = {
> &destroy_by_rcu_attr.attr,
> &shrink_attr.attr,
> &reserved_attr.attr,
> +#ifdef CONFIG_SLUB_CPU_PARTIAL
> &slabs_cpu_partial_attr.attr,
> +#endif
> #ifdef CONFIG_SLUB_DEBUG
> &total_objects_attr.attr,
> &slabs_attr.attr,