From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f42.google.com (mail-wg0-f42.google.com [74.125.82.42]) by kanga.kvack.org (Postfix) with ESMTP id D15DC6B00D8 for ; Tue, 19 May 2015 13:10:08 -0400 (EDT) Received: by wgfl8 with SMTP id l8so25464540wgf.2 for ; Tue, 19 May 2015 10:10:08 -0700 (PDT) Received: from shadbolt.e.decadent.org.uk (shadbolt.e.decadent.org.uk. [88.96.1.126]) by mx.google.com with ESMTPS id el3si16696795wid.68.2015.05.19.10.10.06 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 19 May 2015 10:10:07 -0700 (PDT) Message-ID: <1432055392.12412.34.camel@decadent.org.uk> Subject: Re: [PATCH] mm, memcg: Optionally disable memcg by default using Kconfig From: Ben Hutchings Date: Tue, 19 May 2015 18:09:52 +0100 In-Reply-To: <20150519151541.GJ6203@dhcp22.suse.cz> References: <20150519104057.GC2462@suse.de> <20150519141807.GA9788@cmpxchg.org> <20150519144345.GF2462@suse.de> <20150519151541.GJ6203@dhcp22.suse.cz> Content-Type: multipart/signed; micalg="pgp-sha512"; protocol="application/pgp-signature"; boundary="=-jE7Fec7qAhbXZf0Hnv5Q" Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Mel Gorman , Johannes Weiner , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Tejun Heo , cgroups@vger.kernel.org, Debian kernel maintainers --=-jE7Fec7qAhbXZf0Hnv5Q Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, 2015-05-19 at 17:15 +0200, Michal Hocko wrote: > [Let's CC Ben here - the email thread has started here: > http://marc.info/?l=3Dlinux-mm&m=3D143203206402073&w=3D2 and it seems Deb= ian > is disabling memcg controller already so this might be of your interest] >=20 > 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. >=20 > I've read through > https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=3D534964 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=3D534964#152). This is > no longer the case since 1306a85aed3e ("mm: embed the memcg pointer > directly into struct page") merged in 3.19. >=20 > I can see some point in disabling the memcg due to runtime overhead. I was also concerned about 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)? I have been meaning to reevaluate this as I know the overhead has been reduced. Given Mel's benchmark results, I favour keeping it disabled by default in Debian. So I would welcome this change. Ben. --=20 Ben Hutchings I'm not a reverse psychological virus. Please don't copy me into your sig. --=-jE7Fec7qAhbXZf0Hnv5Q Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIVAwUAVVtuZee/yOyVhhEJAQoIMRAAlIH39TrYgnVzaO/Uycqy23LZpvz4el4d bsjUl6cZM78rlDZJSgcvsHxValZw/0SosW8kvo+S0xzQQLGJGnAFsyoCdtD4k4cj bxYW3k2yxJAOlzq7yBu6xf2s/rMAn/msyPmjqS9lU+ilvOrsxr38odYJMWY8plF2 MEJ2WTaDrspGDM/VeMQlJDw6nSzckJ7p12LodJbLre0souoxRjDzU+90fYJ5kd8a DLonrL+kL+HKxjY/jLtaQVTU8EAIRoxTPDSZaX5myTnxwOI6yLmFKg2N3kO7oB8C aY0pGWD6cjLSxdRwooVmk/Xenzwam1hHWc/12l6XOkaUs43/Xw096mYs9qv3Knhv UGNluf3Flbz+zMM7dg+UaK9jq1kPEWP/jqty4ICnRlKbSTTOtoTtLRKwAKL5bSj5 CAye+w2m77ipEJ2NxNweEsTCCxaniOvqX+IyDiPzkVTlYChaIWQfsD9hsW2Zc7T5 /2mia5f6iEeWjm/3R2MY697a1XXHj1rHAdVg5Yh0K3LE0nqNvnYZPN8pw0ab8ktz /PnVFA+ObAn+n+VBahoDdwdR/rwuXm3a5OnT32s0K9uJtOZRj+hrHkMlGVGX1II0 XLi/rBtNn9om3bvs64TX62+8HdD9v3XveeOOcvQEOAuX2MnGjjTAzg9gO4QM0uvL ZUAZvHEOCRs= =ZIn5 -----END PGP SIGNATURE----- --=-jE7Fec7qAhbXZf0Hnv5Q-- -- 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