From: Sha Zhengju <handai.szj@xxxxxxxxxx> It's inspired by a similar optimization from Glauber Costa (memcg: make it suck faster; https://lkml.org/lkml/2012/9/25/154). Here we use jump label to patch the memcg page stat accounting code in or out when not used. when the first non-root memcg comes to life the code is patching in otherwise it is out. Signed-off-by: Sha Zhengju <handai.szj@xxxxxxxxxx> --- include/linux/memcontrol.h | 9 +++++++++ mm/memcontrol.c | 8 ++++++++ 2 files changed, 17 insertions(+) diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h index 1d22b81..3c4430c 100644 --- a/include/linux/memcontrol.h +++ b/include/linux/memcontrol.h @@ -56,6 +56,9 @@ struct mem_cgroup_reclaim_cookie { }; #ifdef CONFIG_MEMCG + +extern struct static_key memcg_in_use_key; + /* * All "charge" functions with gfp_mask should use GFP_KERNEL or * (gfp_mask & GFP_RECLAIM_MASK). In current implementatin, memcg doesn't @@ -158,6 +161,9 @@ extern atomic_t memcg_moving; static inline void mem_cgroup_begin_update_page_stat(struct page *page, bool *locked, unsigned long *flags) { + if (!static_key_false(&memcg_in_use_key)) + return; + if (mem_cgroup_disabled()) return; rcu_read_lock(); @@ -171,6 +177,9 @@ void __mem_cgroup_end_update_page_stat(struct page *page, static inline void mem_cgroup_end_update_page_stat(struct page *page, bool *locked, unsigned long *flags) { + if (!static_key_false(&memcg_in_use_key)) + return; + if (mem_cgroup_disabled()) return; if (*locked) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 0cb5187..a2f73d7 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -531,6 +531,8 @@ enum res_type { #define MEM_CGROUP_RECLAIM_SHRINK_BIT 0x1 #define MEM_CGROUP_RECLAIM_SHRINK (1 << MEM_CGROUP_RECLAIM_SHRINK_BIT) +struct static_key memcg_in_use_key; + static void mem_cgroup_get(struct mem_cgroup *memcg); static void mem_cgroup_put(struct mem_cgroup *memcg); @@ -2226,6 +2228,9 @@ void mem_cgroup_update_page_stat(struct page *page, struct page_cgroup *pc = lookup_page_cgroup(page); unsigned long uninitialized_var(flags); + if (!static_key_false(&memcg_in_use_key)) + return; + if (mem_cgroup_disabled()) return; @@ -6340,6 +6345,8 @@ mem_cgroup_css_alloc(struct cgroup *cont) parent = mem_cgroup_from_cont(cont->parent); memcg->use_hierarchy = parent->use_hierarchy; memcg->oom_kill_disable = parent->oom_kill_disable; + + static_key_slow_inc(&memcg_in_use_key); } if (parent && parent->use_hierarchy) { @@ -6407,6 +6414,7 @@ static void mem_cgroup_css_free(struct cgroup *cont) kmem_cgroup_destroy(memcg); memcg_dangling_add(memcg); + static_key_slow_dec(&memcg_in_use_key); mem_cgroup_put(memcg); } -- 1.7.9.5 -- 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>