From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f67.google.com (mail-wm0-f67.google.com [74.125.82.67]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3tMr1F3NM6zDvjG for ; Tue, 22 Nov 2016 01:03:45 +1100 (AEDT) Received: by mail-wm0-f67.google.com with SMTP id g23so2295303wme.1 for ; Mon, 21 Nov 2016 06:03:45 -0800 (PST) Date: Mon, 21 Nov 2016 15:03:41 +0100 From: Michal Hocko To: Balbir Singh Cc: mpe@ellerman.id.au, hannes@cmpxchg.org, vdavydov.dev@gmail.com, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, Tejun Heo , Andrew Morton Subject: Re: [RESEND][v1 0/3] Support memory cgroup hotplug Message-ID: <20161121140340.GC18112@dhcp22.suse.cz> References: <1479253501-26261-1-git-send-email-bsingharora@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1479253501-26261-1-git-send-email-bsingharora@gmail.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Wed 16-11-16 10:44:58, Balbir Singh wrote: > In the absence of hotplug we use extra memory proportional to > (possible_nodes - online_nodes) * number_of_cgroups. PPC64 has a patch > to disable large consumption with large number of cgroups. This patch > adds hotplug support to memory cgroups and reverts the commit that > limited possible nodes to online nodes. I didn't get to read patches yet (I am currently swamped by emails after longer vacation so bear with me) but this doesn't tell us _why_ we want this and how much we can actaully save. In general being dynamic is more complex and most systems tend to have possible_nodes close to online_nodes in my experience (well at least on most reasonable architectures). I would also appreciate some highlevel description of the implications. E.g. how to we synchronize with the hotplug operations when iterating node specific data structures. Thanks! -- Michal Hocko SUSE Labs