From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-bk0-f45.google.com (mail-bk0-f45.google.com [209.85.214.45]) by kanga.kvack.org (Postfix) with ESMTP id 476C96B0055 for ; Tue, 11 Mar 2014 21:29:05 -0400 (EDT) Received: by mail-bk0-f45.google.com with SMTP id na10so1387103bkb.32 for ; Tue, 11 Mar 2014 18:29:04 -0700 (PDT) Received: from zene.cmpxchg.org (zene.cmpxchg.org. [2a01:238:4224:fa00:ca1f:9ef3:caee:a2bd]) by mx.google.com with ESMTPS id yj4si9801082bkb.337.2014.03.11.18.29.03 for (version=TLSv1 cipher=RC4-SHA bits=128/128); Tue, 11 Mar 2014 18:29:04 -0700 (PDT) From: Johannes Weiner Subject: [patch 7/8] memcg: do not replicate get_mem_cgroup_from_mm in __mem_cgroup_try_charge Date: Tue, 11 Mar 2014 21:28:33 -0400 Message-Id: <1394587714-6966-8-git-send-email-hannes@cmpxchg.org> In-Reply-To: <1394587714-6966-1-git-send-email-hannes@cmpxchg.org> References: <1394587714-6966-1-git-send-email-hannes@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Michal Hocko , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org From: Michal Hocko __mem_cgroup_try_charge duplicates get_mem_cgroup_from_mm for charges which came without a memcg. The only reason seems to be a tiny optimization when css_tryget is not called if the charge can be consumed from the stock. Nevertheless css_tryget is very cheap since it has been reworked to use per-cpu counting so this optimization doesn't give us anything these days. So let's drop the code duplication so that the code is more readable. Signed-off-by: Michal Hocko Signed-off-by: Johannes Weiner --- mm/memcontrol.c | 50 ++++++-------------------------------------------- 1 file changed, 6 insertions(+), 44 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index cc7f3ca3ef34..4f7192bfa5fa 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2731,52 +2731,14 @@ static int __mem_cgroup_try_charge(struct mm_struct *mm, again: if (*ptr) { /* css should be a valid one */ memcg = *ptr; - if (mem_cgroup_is_root(memcg)) - goto done; - if (consume_stock(memcg, nr_pages)) - goto done; css_get(&memcg->css); } else { - struct task_struct *p; - - rcu_read_lock(); - p = rcu_dereference(mm->owner); - /* - * Because we don't have task_lock(), "p" can exit. - * In that case, "memcg" can point to root or p can be NULL with - * race with swapoff. Then, we have small risk of mis-accouning. - * But such kind of mis-account by race always happens because - * we don't have cgroup_mutex(). It's overkill and we allo that - * small race, here. - * (*) swapoff at el will charge against mm-struct not against - * task-struct. So, mm->owner can be NULL. - */ - memcg = mem_cgroup_from_task(p); - if (!memcg) - memcg = root_mem_cgroup; - if (mem_cgroup_is_root(memcg)) { - rcu_read_unlock(); - goto done; - } - if (consume_stock(memcg, nr_pages)) { - /* - * It seems dagerous to access memcg without css_get(). - * But considering how consume_stok works, it's not - * necessary. If consume_stock success, some charges - * from this memcg are cached on this cpu. So, we - * don't need to call css_get()/css_tryget() before - * calling consume_stock(). - */ - rcu_read_unlock(); - goto done; - } - /* after here, we may be blocked. we need to get refcnt */ - if (!css_tryget(&memcg->css)) { - rcu_read_unlock(); - goto again; - } - rcu_read_unlock(); + memcg = get_mem_cgroup_from_mm(mm); } + if (mem_cgroup_is_root(memcg)) + goto done; + if (consume_stock(memcg, nr_pages)) + goto done; do { bool invoke_oom = oom && !nr_oom_retries; @@ -2812,8 +2774,8 @@ again: if (batch > nr_pages) refill_stock(memcg, batch - nr_pages); - css_put(&memcg->css); done: + css_put(&memcg->css); *ptr = memcg; return 0; nomem: -- 1.9.0 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org