On Thu 23-02-17 14:36:39, Laurent Dufour wrote:
> Until a soft limit is set to a cgroup, the soft limit data are useless
> so delay this allocation when a limit is set.
Hmm, I am still undecided whether this is actually worth it. On one hand
distribution kernels tend to have quite large NUMA_SHIFT (e.g. SLES has
NUMA_SHIFT=10 and then we will save 8kB+12kB which is not hell of a lot
but always good if we can save that, especially for a rarely used
feature. The code grown on the other hand (it was in __init section
previously) which is a minus, on the other hand.
What do you think Johannes?
This would be a useful info in the changelog, btw.
> Suggested-by: Michal Hocko <mhocko@xxxxxxxxxx>
> Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx>
The patch looks good to me so feel free to add
Reviewed-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> mm/memcontrol.c | 67 ++++++++++++++++++++++++++++++++++++++++++++-------------
> 1 file changed, 52 insertions(+), 15 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index a9f10fde44a6..c639c898809d 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -142,7 +142,7 @@ struct mem_cgroup_tree {
> struct mem_cgroup_tree_per_node *rb_tree_per_node[MAX_NUMNODES];
> };
>
> -static struct mem_cgroup_tree soft_limit_tree __read_mostly;
> +static struct mem_cgroup_tree *soft_limit_tree __read_mostly;
>
> /* for OOM */
> struct mem_cgroup_eventfd_list {
> @@ -381,10 +381,52 @@ mem_cgroup_page_nodeinfo(struct mem_cgroup *memcg, struct page *page)
> return memcg->nodeinfo[nid];
> }
>
> +static bool soft_limit_initialize(void)
> +{
> + static DEFINE_MUTEX(soft_limit_mutex);
> + struct mem_cgroup_tree *tree;
> + bool ret = true;
> + int node;
> +
> + mutex_lock(&soft_limit_mutex);
> + if (soft_limit_tree)
> + goto bail;
> +
> + tree = kmalloc(sizeof(*soft_limit_tree), GFP_KERNEL);
> + if (!tree) {
> + ret = false;
> + goto bail;
> + }
> + for_each_node(node) {
> + struct mem_cgroup_tree_per_node *rtpn;
> +
> + rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL,
> + node_online(node) ? node : NUMA_NO_NODE);
> + if (!rtpn)
> + goto cleanup;
> +
> + rtpn->rb_root = RB_ROOT;
> + spin_lock_init(&rtpn->lock);
> + tree->rb_tree_per_node[node] = rtpn;
> + }
> + WRITE_ONCE(soft_limit_tree, tree);
> +bail:
> + mutex_unlock(&soft_limit_mutex);
> + return ret;
> +cleanup:
> + for_each_node(node)
> + kfree(tree->rb_tree_per_node[node]);
> + kfree(tree);
> + ret = false;
> + goto bail;
> +}
> +
> static struct mem_cgroup_tree_per_node *
> soft_limit_tree_node(int nid)
> {
> - return soft_limit_tree.rb_tree_per_node[nid];
> + if (!soft_limit_tree)
> + return NULL;
> + return soft_limit_tree->rb_tree_per_node[nid];
> }
>
> static struct mem_cgroup_tree_per_node *
> @@ -392,7 +434,9 @@ soft_limit_tree_from_page(struct page *page)
> {
> int nid = page_to_nid(page);
>
> - return soft_limit_tree.rb_tree_per_node[nid];
> + if (!soft_limit_tree)
> + return NULL;
> + return soft_limit_tree->rb_tree_per_node[nid];
> }
>
> static void __mem_cgroup_insert_exceeded(struct mem_cgroup_per_node *mz,
> @@ -3003,6 +3047,10 @@ static ssize_t mem_cgroup_write(struct kernfs_open_file *of,
> }
> break;
> case RES_SOFT_LIMIT:
> + if (!soft_limit_initialize()) {
> + ret = -ENOMEM;
> + break;
> + }
> memcg->soft_limit = nr_pages;
> ret = 0;
> break;
> @@ -5777,7 +5825,7 @@ __setup("cgroup.memory=", cgroup_memory);
> */
> static int __init mem_cgroup_init(void)
> {
> - int cpu, node;
> + int cpu;
>
> #ifndef CONFIG_SLOB
> /*
> @@ -5797,17 +5845,6 @@ static int __init mem_cgroup_init(void)
> INIT_WORK(&per_cpu_ptr(&memcg_stock, cpu)->work,
> drain_local_stock);
>
> - for_each_node(node) {
> - struct mem_cgroup_tree_per_node *rtpn;
> -
> - rtpn = kzalloc_node(sizeof(*rtpn), GFP_KERNEL,
> - node_online(node) ? node : NUMA_NO_NODE);
> -
> - rtpn->rb_root = RB_ROOT;
> - spin_lock_init(&rtpn->lock);
> - soft_limit_tree.rb_tree_per_node[node] = rtpn;
> - }
> -
> return 0;
> }
> subsys_initcall(mem_cgroup_init);
> --
> 2.7.4
--
Michal Hocko
SUSE Labs
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