Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759715AbbKTK7T (ORCPT ); Fri, 20 Nov 2015 05:59:19 -0500 Received: from mx2.parallels.com ([199.115.105.18]:39246 "EHLO mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759592AbbKTK7O (ORCPT ); Fri, 20 Nov 2015 05:59:14 -0500 Date: Fri, 20 Nov 2015 13:58:57 +0300 From: Vladimir Davydov To: Johannes Weiner CC: David Miller , Andrew Morton , Tejun Heo , Michal Hocko , , , , , Subject: Re: [PATCH 08/14] net: tcp_memcontrol: sanitize tcp memory accounting callbacks Message-ID: <20151120105857.GB31308@esperanza> References: <1447371693-25143-1-git-send-email-hannes@cmpxchg.org> <1447371693-25143-9-git-send-email-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <1447371693-25143-9-git-send-email-hannes@cmpxchg.org> X-ClientProxiedBy: US-EXCH.sw.swsoft.com (10.255.249.47) To US-EXCH2.sw.swsoft.com (10.255.249.46) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2299 Lines: 42 On Thu, Nov 12, 2015 at 06:41:27PM -0500, Johannes Weiner wrote: > There won't be a tcp control soft limit, so integrating the memcg code > into the global skmem limiting scheme complicates things > unnecessarily. Replace this with simple and clear charge and uncharge > calls--hidden behind a jump label--to account skb memory. > > Note that this is not purely aesthetic: as a result of shoehorning the > per-memcg code into the same memory accounting functions that handle > the global level, the old code would compare the per-memcg consumption > against the smaller of the per-memcg limit and the global limit. This > allowed the total consumption of multiple sockets to exceed the global > limit, as long as the individual sockets stayed within bounds. After > this change, the code will always compare the per-memcg consumption to > the per-memcg limit, and the global consumption to the global limit, > and thus close this loophole. > > Without a soft limit, the per-memcg memory pressure state in sockets > is generally questionable. However, we did it until now, so we > continue to enter it when the hard limit is hit, and packets are > dropped, to let other sockets in the cgroup know that they shouldn't > grow their transmit windows, either. However, keep it simple in the > new callback model and leave memory pressure lazily when the next > packet is accepted (as opposed to doing it synchroneously when packets > are processed). When packets are dropped, network performance will > already be in the toilet, so that should be a reasonable trade-off. > > As described above, consumption is now checked on the per-memcg level > and the global level separately. Likewise, memory pressure states are > maintained on both the per-memcg level and the global level, and a > socket is considered under pressure when either level asserts as much. > > Signed-off-by: Johannes Weiner It leaves the legacy functionality intact, while making the code look much better. Reviewed-by: Vladimir Davydov -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/