From mboxrd@z Thu Jan 1 00:00:00 1970 From: Roman Gushchin Subject: [PATCH RFC 1/2] mm: kmem: optimize get_obj_cgroup_from_current() Date: Tue, 20 Dec 2022 10:27:44 -0800 Message-ID: <20221220182745.1903540-2-roman.gushchin@linux.dev> References: <20221220182745.1903540-1-roman.gushchin@linux.dev> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1671560883; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=1c+efmi7i1PNMb6NmmQf0Ro/sE7SMscFhY/KBS3yOLk=; b=Wx7bQ5ioJAD+g491R7nSJvJ8QTYMx+OPD/+3NQf2xDyjGmSAIeS5xvA6vaaypoUUowSvau T38EBM/MyoOs0D9shUHdyPMcOMxI88n+BDtB5+ZeMySUKoKja9i+0tgo8ESPYw+WmPupoG JdpUiHXhDx7tLpgzdmFRX6vTZ0dwRYM= In-Reply-To: <20221220182745.1903540-1-roman.gushchin-fxUVXftIFDnyG1zEObXtfA@public.gmane.org> List-ID: Content-Type: text/plain; charset="us-ascii" To: linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Shakeel Butt , Johannes Weiner , Michal Hocko , Muchun Song , Andrew Morton , Roman Gushchin Manually inline memcg_kmem_bypass() and active_memcg() to speed up get_obj_cgroup_from_current() by avoiding duplicate in_task() checks and active_memcg() readings. Also add a likely() macro to __get_obj_cgroup_from_memcg(): obj_cgroup_tryget() should succeed at almost all times except a very unlikely race with the memcg deletion path. Signed-off-by: Roman Gushchin --- mm/memcontrol.c | 34 ++++++++++++++-------------------- 1 file changed, 14 insertions(+), 20 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index bafd3cde4507..82828c51d2ea 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1047,19 +1047,6 @@ struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm) } EXPORT_SYMBOL(get_mem_cgroup_from_mm); -static __always_inline bool memcg_kmem_bypass(void) -{ - /* Allow remote memcg charging from any context. */ - if (unlikely(active_memcg())) - return false; - - /* Memcg to charge can't be determined. */ - if (!in_task() || !current->mm || (current->flags & PF_KTHREAD)) - return true; - - return false; -} - /** * mem_cgroup_iter - iterate over memory cgroup hierarchy * @root: hierarchy root @@ -3004,7 +2991,7 @@ static struct obj_cgroup *__get_obj_cgroup_from_memcg(struct mem_cgroup *memcg) for (; !mem_cgroup_is_root(memcg); memcg = parent_mem_cgroup(memcg)) { objcg = rcu_dereference(memcg->objcg); - if (objcg && obj_cgroup_tryget(objcg)) + if (likely(objcg && obj_cgroup_tryget(objcg))) break; objcg = NULL; } @@ -3013,16 +3000,23 @@ static struct obj_cgroup *__get_obj_cgroup_from_memcg(struct mem_cgroup *memcg) __always_inline struct obj_cgroup *get_obj_cgroup_from_current(void) { - struct obj_cgroup *objcg = NULL; struct mem_cgroup *memcg; + struct obj_cgroup *objcg; - if (memcg_kmem_bypass()) - return NULL; + if (in_task()) { + memcg = current->active_memcg; + + /* Memcg to charge can't be determined. */ + if (likely(!memcg) && (!current->mm || (current->flags & PF_KTHREAD))) + return NULL; + } else { + memcg = this_cpu_read(int_active_memcg); + if (likely(!memcg)) + return NULL; + } rcu_read_lock(); - if (unlikely(active_memcg())) - memcg = active_memcg(); - else + if (!memcg) memcg = mem_cgroup_from_task(current); objcg = __get_obj_cgroup_from_memcg(memcg); rcu_read_unlock(); -- 2.39.0