On Wed, 23 Jan 2013 21:33:46 +0400
Glauber Costa <glommer@xxxxxxxxxxxxx> wrote:
> In order to maintain all the memcg bookkeeping, we need per-node
> descriptors, which will in turn contain a per-zone descriptor.
>
> Because we want to statically allocate those, this array ends up being
> very big. Part of the reason is that we allocate something large enough
> to hold MAX_NUMNODES, the compile time constant that holds the maximum
> number of nodes we would ever consider.
>
> However, we can do better in some cases if the firmware help us. This is
> true for modern x86 machines; coincidentally one of the architectures in
> which MAX_NUMNODES tends to be very big.
>
> By using the firmware-provided maximum number of nodes instead of
> MAX_NUMNODES, we can reduce the memory footprint of struct memcg
> considerably. In the extreme case in which we have only one node, this
> reduces the size of the structure from ~ 64k to ~2k. This is
> particularly important because it means that we will no longer resort to
> the vmalloc area for the struct memcg on defconfigs. We also have enough
> room for an extra node and still be outside vmalloc.
>
> One also has to keep in mind that with the industry's ability to fit
> more processors in a die as fast as the FED prints money, a nodes = 2
> configuration is already respectably big.
Seems sensible.
> +static inline int memcg_size(void)
> +{
> + return sizeof(struct mem_cgroup) +
> + nr_node_ids * sizeof(struct mem_cgroup_per_node);
> +}
> +
> /* internal only representation about the status of kmem accounting. */
> enum {
> KMEM_ACCOUNTED_ACTIVE = 0, /* accounted by this cgroup itself */
> @@ -5894,9 +5904,9 @@ static void free_mem_cgroup_per_zone_info(struct mem_cgroup *memcg, int node)
> static struct mem_cgroup *mem_cgroup_alloc(void)
> {
> struct mem_cgroup *memcg;
> - int size = sizeof(struct mem_cgroup);
> + int size = memcg_size();
>
> - /* Can be very big if MAX_NUMNODES is very big */
> + /* Can be very big if nr_node_ids is very big */
> if (size < PAGE_SIZE)
> memcg = kzalloc(size, GFP_KERNEL);
> else
> @@ -5933,7 +5943,7 @@ out_free:
> static void __mem_cgroup_free(struct mem_cgroup *memcg)
> {
> int node;
> - int size = sizeof(struct mem_cgroup);
> + int size = memcg_size();
>
> mem_cgroup_remove_from_trees(memcg);
> free_css_id(&mem_cgroup_subsys, &memcg->css);
Really everything here should be using size_t - a minor
cosmetic/readability thing.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>