From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759662Ab0KRQXB (ORCPT ); Thu, 18 Nov 2010 11:23:01 -0500 Received: from gir.skynet.ie ([193.1.99.77]:56170 "EHLO gir.skynet.ie" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754115Ab0KRQXA (ORCPT ); Thu, 18 Nov 2010 11:23:00 -0500 Date: Thu, 18 Nov 2010 16:22:45 +0000 From: Mel Gorman To: Andrea Arcangeli Cc: KOSAKI Motohiro , linux-mm@kvack.org, Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, Marcelo Tosatti , Adam Litke , Avi Kivity , Hugh Dickins , Rik van Riel , Dave Hansen , Benjamin Herrenschmidt , Ingo Molnar , Mike Travis , KAMEZAWA Hiroyuki , Christoph Lameter , Chris Wright , bpicco@redhat.com, Balbir Singh , "Michael S. Tsirkin" , Peter Zijlstra , Johannes Weiner , Daisuke Nishimura , Chris Mason , Borislav Petkov Subject: Re: [PATCH 55 of 66] select CONFIG_COMPACTION if TRANSPARENT_HUGEPAGE enabled Message-ID: <20101118162245.GE8135@csn.ul.ie> References: <89a62752012298bb500c.1288798110@v2.random> <20101109151756.BC7B.A69D9226@jp.fujitsu.com> <20101109211145.GB6809@random.random> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20101109211145.GB6809@random.random> User-Agent: Mutt/1.5.17+20080114 (2008-01-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Nov 09, 2010 at 10:11:45PM +0100, Andrea Arcangeli wrote: > On Tue, Nov 09, 2010 at 03:20:33PM +0900, KOSAKI Motohiro wrote: > > > From: Andrea Arcangeli > > > > > > With transparent hugepage support we need compaction for the "defrag" sysfs > > > controls to be effective. > > > > > > Signed-off-by: Andrea Arcangeli > > > --- > > > > > > diff --git a/mm/Kconfig b/mm/Kconfig > > > --- a/mm/Kconfig > > > +++ b/mm/Kconfig > > > @@ -305,6 +305,7 @@ config NOMMU_INITIAL_TRIM_EXCESS > > > config TRANSPARENT_HUGEPAGE > > > bool "Transparent Hugepage Support" > > > depends on X86 && MMU > > > + select COMPACTION > > > help > > > Transparent Hugepages allows the kernel to use huge pages and > > > huge tlb transparently to the applications whenever possible. > > > > I dislike this. THP and compaction are completely orthogonal. I think > > you are talking only your performance recommendation. I mean I dislike > > Kconfig 'select' hell and I hope every developers try to avoid it as > > far as possible. > > At the moment THP hangs the system if COMPACTION isn't selected Just to confirm - by hang, you mean grinds to a slow pace as opposed to coming to a complete stop and having to restart? If so then Acked-by: Mel Gorman > (please try yourself if you don't believe), as without COMPACTION > lumpy reclaim wouldn't be entirely disabled. So at the moment it's not > orthogonal. When lumpy will be removed from the VM (like I tried > multiple times to achieve) I can remove the select COMPACTION in > theory, but then 99% of THP users would be still doing a mistake in > disabling compaction, even if the mistake won't return in fatal > runtime but just slightly degraded performance. > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with ESMTP id E0FF66B0088 for ; Thu, 18 Nov 2010 11:23:05 -0500 (EST) Date: Thu, 18 Nov 2010 16:22:45 +0000 From: Mel Gorman Subject: Re: [PATCH 55 of 66] select CONFIG_COMPACTION if TRANSPARENT_HUGEPAGE enabled Message-ID: <20101118162245.GE8135@csn.ul.ie> References: <89a62752012298bb500c.1288798110@v2.random> <20101109151756.BC7B.A69D9226@jp.fujitsu.com> <20101109211145.GB6809@random.random> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20101109211145.GB6809@random.random> Sender: owner-linux-mm@kvack.org To: Andrea Arcangeli Cc: KOSAKI Motohiro , linux-mm@kvack.org, Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, Marcelo Tosatti , Adam Litke , Avi Kivity , Hugh Dickins , Rik van Riel , Dave Hansen , Benjamin Herrenschmidt , Ingo Molnar , Mike Travis , KAMEZAWA Hiroyuki , Christoph Lameter , Chris Wright , bpicco@redhat.com, Balbir Singh , "Michael S. Tsirkin" , Peter Zijlstra , Johannes Weiner , Daisuke Nishimura , Chris Mason , Borislav Petkov List-ID: On Tue, Nov 09, 2010 at 10:11:45PM +0100, Andrea Arcangeli wrote: > On Tue, Nov 09, 2010 at 03:20:33PM +0900, KOSAKI Motohiro wrote: > > > From: Andrea Arcangeli > > > > > > With transparent hugepage support we need compaction for the "defrag" sysfs > > > controls to be effective. > > > > > > Signed-off-by: Andrea Arcangeli > > > --- > > > > > > diff --git a/mm/Kconfig b/mm/Kconfig > > > --- a/mm/Kconfig > > > +++ b/mm/Kconfig > > > @@ -305,6 +305,7 @@ config NOMMU_INITIAL_TRIM_EXCESS > > > config TRANSPARENT_HUGEPAGE > > > bool "Transparent Hugepage Support" > > > depends on X86 && MMU > > > + select COMPACTION > > > help > > > Transparent Hugepages allows the kernel to use huge pages and > > > huge tlb transparently to the applications whenever possible. > > > > I dislike this. THP and compaction are completely orthogonal. I think > > you are talking only your performance recommendation. I mean I dislike > > Kconfig 'select' hell and I hope every developers try to avoid it as > > far as possible. > > At the moment THP hangs the system if COMPACTION isn't selected Just to confirm - by hang, you mean grinds to a slow pace as opposed to coming to a complete stop and having to restart? If so then Acked-by: Mel Gorman > (please try yourself if you don't believe), as without COMPACTION > lumpy reclaim wouldn't be entirely disabled. So at the moment it's not > orthogonal. When lumpy will be removed from the VM (like I tried > multiple times to achieve) I can remove the select COMPACTION in > theory, but then 99% of THP users would be still doing a mistake in > disabling compaction, even if the mistake won't return in fatal > runtime but just slightly degraded performance. > -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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/ . Fight unfair telecom policy in Canada: sign http://dissolvethecrtc.ca/ Don't email: email@kvack.org