Re: [PATCH] mm/slub: skip node in case there is no slab to acquire

[Michal Hocko <mhocko@kernel.org>]

On Thu 08-11-18 09:12:04, Wei Yang wrote:
> for_each_zone_zonelist() iterates the zonelist one by one, which means
> it will iterate on zones on the same node. While get_partial_node()
> checks available slab on node base instead of zone.
> 
> This patch skip a node in case get_partial_node() fails to acquire slab
> on that node.

If this is an optimization then it should be accompanied by some
numbers.

> @@ -1882,6 +1882,9 @@ static void *get_any_partial(struct kmem_cache *s, gfp_t flags,
>  	enum zone_type high_zoneidx = gfp_zone(flags);
>  	void *object;
>  	unsigned int cpuset_mems_cookie;
> +	nodemask_t nmask = node_states[N_MEMORY];

This will allocate a large bitmask on the stack and that is no-go for
something that might be called from a potentially deep call stack
already. Also are you sure that the micro-optimization offsets the
copying overhead?

-- 
Michal Hocko
SUSE Labs