From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail137.messagelabs.com (mail137.messagelabs.com [216.82.249.19]) by kanga.kvack.org (Postfix) with SMTP id 77CB68D0001 for ; Sun, 14 Nov 2010 00:07:12 -0500 (EST) Received: from m4.gw.fujitsu.co.jp ([10.0.50.74]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id oAE579mt001533 for (envelope-from kosaki.motohiro@jp.fujitsu.com); Sun, 14 Nov 2010 14:07:10 +0900 Received: from smail (m4 [127.0.0.1]) by outgoing.m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 52B2C45DE7D for ; Sun, 14 Nov 2010 14:07:09 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (s4.gw.fujitsu.co.jp [10.0.50.94]) by m4.gw.fujitsu.co.jp (Postfix) with ESMTP id 1072545DE4D for ; Sun, 14 Nov 2010 14:07:09 +0900 (JST) Received: from s4.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id E04E81DB8040 for ; Sun, 14 Nov 2010 14:07:08 +0900 (JST) Received: from m105.s.css.fujitsu.com (m105.s.css.fujitsu.com [10.249.87.105]) by s4.gw.fujitsu.co.jp (Postfix) with ESMTP id 8DA1C1DB803B for ; Sun, 14 Nov 2010 14:07:08 +0900 (JST) From: KOSAKI Motohiro Subject: Re: [PATCH 55 of 66] select CONFIG_COMPACTION if TRANSPARENT_HUGEPAGE enabled In-Reply-To: <20101109211145.GB6809@random.random> References: <20101109151756.BC7B.A69D9226@jp.fujitsu.com> <20101109211145.GB6809@random.random> Message-Id: <20101111091220.9941.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset="ISO-2022-JP" Content-Transfer-Encoding: 7bit Date: Sun, 14 Nov 2010 14:07:07 +0900 (JST) Sender: owner-linux-mm@kvack.org To: Andrea Arcangeli Cc: kosaki.motohiro@jp.fujitsu.com, linux-mm@kvack.org, Linus Torvalds , Andrew Morton , linux-kernel@vger.kernel.org, Marcelo Tosatti , Adam Litke , Avi Kivity , Hugh Dickins , Rik van Riel , Mel Gorman , 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 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 > (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. ok, I beleive you. but please add this reason to the description. -- 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