Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753554AbaJIBpb (ORCPT ); Wed, 8 Oct 2014 21:45:31 -0400 Received: from mail9.hitachi.co.jp ([133.145.228.44]:35659 "EHLO mail9.hitachi.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751223AbaJIBpX (ORCPT ); Wed, 8 Oct 2014 21:45:23 -0400 Message-ID: <5435E8AB.7030103@hitachi.com> Date: Thu, 09 Oct 2014 10:45:15 +0900 From: Masami Hiramatsu Organization: Hitachi, Ltd., Japan User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:13.0) Gecko/20120614 Thunderbird/13.0.1 MIME-Version: 1.0 To: Chuck Ebbert Cc: Chris Wilson , linux-kernel@vger.kernel.org, Jiri Kosina , "H. Peter Anvin" , Steven Rostedt , Jason Baron , yrl.pp-manager.tt@hitachi.com, Borislav Petkov , Ingo Molnar , Daniel Vetter Subject: Re: i915.ko WC writes are slow after ea8596bb2d8d379 References: <20141008090336.GD12897@nuc-i3427.alporthouse.com> <20141008124705.793d652d@as> In-Reply-To: <20141008124705.793d652d@as> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org (2014/10/09 2:47), Chuck Ebbert wrote: > On Wed, 8 Oct 2014 10:03:36 +0100 > Chris Wilson wrote: > >> and adding that back into the current build, e.g. >> >> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig >> index 3632743..48a8a69 100644 >> --- a/arch/x86/Kconfig >> +++ b/arch/x86/Kconfig >> @@ -87,6 +87,7 @@ config X86 >> select HAVE_USER_RETURN_NOTIFIER >> select ARCH_BINFMT_ELF_RANDOMIZE_PIE >> select HAVE_ARCH_JUMP_LABEL >> + select STOP_MACHINE >> select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE >> select SPARSE_IRQ >> select GENERIC_FIND_FIRST_BIT >> >> fixes the regression. >> > > Looking closer at this, it seems most configs work by accident, > because they have MOD_UNLOAD and/or HOTPLUG_CPU enabled. I take it > you disabled both of those? stop_machine() is called from all kinds > of places and almost none of them make sure STOP_MACHINE is selected. I guess most of them expects stop_machine() is not a configurable feature... If some of them requires stop_machine(), it should enable it on its kconfig entry (including ftrace, kprobes). > $ find -name Kconf\* | xargs grep STOP_MACHINE > ./init/Kconfig:config STOP_MACHINE > > All these places use stop_machine(): > > mm/page_alloc.c, line 3886 > drivers/xen/manage.c, line 130 > drivers/char/hw_random/intel-rng.c, line 373 > arch/powerpc/mm/numa.c: > line 1616 > line 1623 > arch/powerpc/platforms/powernv/subcore.c, line 324 > arch/arm/kernel/kprobes.c, line 165 > arch/arm/kernel/patch.c: > line 64 > line 71 > arch/s390/kernel/jump_label.c, line 61 > arch/s390/kernel/kprobes.c: > line 311 > line 320 > arch/s390/kernel/time.c: > line 820 > line 1590 > arch/x86/kernel/cpu/mtrr/main.c, line 231 > arch/arm64/kernel/insn.c, line 181 > kernel/time/timekeeping.c, line 892 > kernel/trace/ftrace.c, line 2219 > kernel/module.c: > line 770 > line 1861 > BTW, as I sent a series of patches, the last two can be removed. https://lkml.org/lkml/2014/8/25/142 Thank you, -- Masami HIRAMATSU Software Platform Research Dept. Linux Technology Research Center Hitachi, Ltd., Yokohama Research Laboratory E-mail: masami.hiramatsu.pt@hitachi.com -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/