From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michal Hocko Subject: Re: [PATCH] mm, memcg: Optionally disable memcg by default using Kconfig Date: Tue, 19 May 2015 17:15:41 +0200 Message-ID: <20150519151541.GJ6203@dhcp22.suse.cz> References: <20150519104057.GC2462@suse.de> <20150519141807.GA9788@cmpxchg.org> <20150519144345.GF2462@suse.de> Mime-Version: 1.0 Return-path: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; bh=9eb7nQt2cC0VN2+8cch6nYKfi6dHmo23KFN+FWJSUr0=; b=tPoafzIT8FuLqyjFeN+s5y1ZMhpYAIvANckZSjkFXBRB26x56BuaHTEcwwf4xnFxUv QTCxDY+O+PpvYWWUHTmYMEp4uJfkumjsQQdw2BXgyW6ZDN08hCfJV7cqjBE014NtJjAz zTzzezxYhfsR7hY2ZrzNtxkyTjlAZ3vHid+vXb33lQ2/K0jSM8V2P1peigKYkMaVJp7i uieuh2m8aa33xoUWzhCKqFK6ZfMxc6ZFLoLhNbOhxID96evv29R3MWPBVij0+1FrZfYL AnK2YQYLvtm+cMOyi2bNQjNLqZZp48s2YyveHAA3dSHLX0ewxJF4ZsyZgCHNZYaiI72y ghBg== Content-Disposition: inline In-Reply-To: <20150519144345.GF2462@suse.de> Sender: owner-linux-mm@kvack.org List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Mel Gorman Cc: Johannes Weiner , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Tejun Heo , cgroups@vger.kernel.org, Ben Hutchings [Let's CC Ben here - the email thread has started here: http://marc.info/?l=linux-mm&m=143203206402073&w=2 and it seems Debian is disabling memcg controller already so this might be of your interest] On Tue 19-05-15 15:43:45, Mel Gorman wrote: [...] > After I wrote the patch, I spotted that Debian apparently already > does something like this and by coincidence they matched the > parameter name and values. See the memory controller instructions on > https://wiki.debian.org/LXC#Prepare_the_host . So in this case at least > upstream would match something that at least one distro in the field > already uses. I've read through https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=534964 and it seems that the primary motivation for the runtime disabling was the _memory_ overhead of the struct page_cgroup (https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=534964#152). This is no longer the case since 1306a85aed3e ("mm: embed the memcg pointer directly into struct page") merged in 3.19. I can see some point in disabling the memcg due to runtime overhead. There will always be some, albeit hard to notice. If an user really need this to happen there is a command line option for that. The question is who would do CONFIG_MEMCG && !MEMCG_DEFAULT_ENABLED. Do you expect any distributions go that way? Ben, would you welcome such a change upstream or is there a reason to change the Debian kernel runtime default now that the memory overhead is mostly gone (for 3.19+ kernels of course)? -- Michal Hocko SUSE Labs -- 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