From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f50.google.com (mail-pa0-f50.google.com [209.85.220.50]) by kanga.kvack.org (Postfix) with ESMTP id 2E6686B0253 for ; Fri, 20 Nov 2015 05:59:15 -0500 (EST) Received: by pacdm15 with SMTP id dm15so113741623pac.3 for ; Fri, 20 Nov 2015 02:59:14 -0800 (PST) Received: from mx2.parallels.com (mx2.parallels.com. [199.115.105.18]) by mx.google.com with ESMTPS id hq4si18990330pbb.89.2015.11.20.02.59.14 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 20 Nov 2015 02:59:14 -0800 (PST) Date: Fri, 20 Nov 2015 13:58:57 +0300 From: Vladimir Davydov 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> Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: David Miller , Andrew Morton , Tejun Heo , Michal Hocko , netdev@vger.kernel.org, linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@fb.com 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, 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