From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751798AbaJOPSk (ORCPT ); Wed, 15 Oct 2014 11:18:40 -0400 Received: from cantor2.suse.de ([195.135.220.15]:56913 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751447AbaJOPSj (ORCPT ); Wed, 15 Oct 2014 11:18:39 -0400 Date: Wed, 15 Oct 2014 17:18:36 +0200 From: Michal Hocko To: Johannes Weiner Cc: Andrew Morton , Vladimir Davydov , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [patch 2/5] mm: memcontrol: take a css reference for each charged page Message-ID: <20141015151836.GG23547@dhcp22.suse.cz> References: <1413303637-23862-1-git-send-email-hannes@cmpxchg.org> <1413303637-23862-3-git-send-email-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1413303637-23862-3-git-send-email-hannes@cmpxchg.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 14-10-14 12:20:34, Johannes Weiner wrote: > Charges currently pin the css indirectly by playing tricks during > css_offline(): user pages stall the offlining process until all of > them have been reparented, whereas kmemcg acquires a keep-alive > reference if outstanding kernel pages are detected at that point. > > In preparation for removing all this complexity, make the pinning > explicit and acquire a css references for every charged page. > > Signed-off-by: Johannes Weiner > Reviewed-by: Vladimir Davydov Acked-by: Michal Hocko > --- > include/linux/cgroup.h | 26 +++++++++++++++++++++++ > include/linux/percpu-refcount.h | 47 +++++++++++++++++++++++++++++++++-------- > mm/memcontrol.c | 21 ++++++++++++++---- > 3 files changed, 81 insertions(+), 13 deletions(-) > [...] > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 67dabe8b0aa6..a3feead6be15 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2256,6 +2256,7 @@ static void drain_stock(struct memcg_stock_pcp *stock) > page_counter_uncharge(&old->memory, stock->nr_pages); > if (do_swap_account) > page_counter_uncharge(&old->memsw, stock->nr_pages); > + css_put_many(&old->css, stock->nr_pages); I have suggested to add a comment about pairing css_get here because the corresponding refill_stock doesn't take any reference which might be little bit confusing. Nothing earth shattering of course... > stock->nr_pages = 0; > } > stock->cached = NULL; > @@ -2513,6 +2514,7 @@ bypass: > return -EINTR; > > done_restock: > + css_get_many(&memcg->css, batch); > if (batch > nr_pages) > refill_stock(memcg, batch - nr_pages); > done: [...] -- Michal Hocko SUSE Labs