From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from lennier.cc.vt.edu ([198.82.162.213]:38604 "EHLO lennier.cc.vt.edu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751578Ab0ALRTA (ORCPT ); Tue, 12 Jan 2010 12:19:00 -0500 Subject: Re: [RFC PATCH 2/4] x86: use dmi check to treat disabled cpus as hotplug cpus. In-Reply-To: Your message of "Tue, 12 Jan 2010 08:26:22 PST." From: Valdis.Kletnieks@vt.edu References: <1263264483-3959-1-git-send-email-yinghai@kernel.org> <1263264483-3959-4-git-send-email-yinghai@kernel.org> <6686.1263312874@localhost> Mime-Version: 1.0 Content-Type: multipart/signed; boundary="==_Exmh_1263316641_4706P"; micalg=pgp-sha1; protocol="application/pgp-signature" Content-Transfer-Encoding: 7bit Date: Tue, 12 Jan 2010 12:17:21 -0500 Message-ID: <23825.1263316641@localhost> Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Linus Torvalds , Roman Zippel , linux-kbuild@vger.kernel.org Cc: Yinghai Lu , Suresh Siddha , "ananth@in.ibm.com" , Ingo Molnar , Thomas Gleixner , "H. Peter Anvin" , Andrew Morton , linux-kernel@vger.kernel.org --==_Exmh_1263316641_4706P Content-Type: text/plain; charset=us-ascii On Tue, 12 Jan 2010 08:26:22 PST, Linus Torvalds said: > > > On Tue, 12 Jan 2010, Valdis.Kletnieks@vt.edu wrote: > > > > OK, I'll bite - how do you build an X86-64 kernel that doesn't have > > CONFIG_HOTPLUG_CPU selected? Try as I might, even if I have PM_SLEEP=n, > > PM_SLEEP_SMP insists on being set, and then selecting HOTPLUG_SMP. > > If that is true, then there is some bug in the kconfig parser. > PM_SLEEP_SMP depends on PM_SLEEP, so with PM_SLEEP=n it should never be > set. So now I go back and check, and it *was* possible to get a PM_SLEEP_SMP=n. Apparently in my previous attempts, I tried turning stuff off and PM_SLEEP_SMP stayed on just like this time as long as I was puttering around in menuconfig. But turning it off, *exiting menuconfig*, and then re-starting menuconfig made it work. Weird. It seems like if something does a 'select' on something that isn't a visible symbol, and the symbol gets toggled, the selects aren't redriven - and since it's not a visible symbol, you can't toggle it yourself. But saving and restarting menuconfig forces a refresh and things start acting right. Adding Roman and the kbuild list to the cc: And turning off PM_SLEEP and HOTPLUG_CPU ended up saving a chunk of memory: Before: % size vmlinux text data bss dec hex filename 8964445 1377200 6094320 16435965 facafd vmlinux After: % size vmlinux text data bss dec hex filename 8889523 1378768 6089648 16357939 f99a33 vmlinux --==_Exmh_1263316641_4706P Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Exmh version 2.5 07/13/2001 iD8DBQFLTK6hcC3lWbTT17ARAoRvAJ0TW6Evs7m772oGTjSLAVp9mO6GRgCgi8wI 3xMwgbNim8z1Z6H/4xNeGaM= =v/5Z -----END PGP SIGNATURE----- --==_Exmh_1263316641_4706P--