Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757735Ab1FVMfF (ORCPT ); Wed, 22 Jun 2011 08:35:05 -0400 Received: from mx1.redhat.com ([209.132.183.28]:1032 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757502Ab1FVMfD (ORCPT ); Wed, 22 Jun 2011 08:35:03 -0400 Message-ID: <4E01E148.2080302@redhat.com> Date: Wed, 22 Jun 2011 20:34:16 +0800 From: Cong Wang User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc14 Thunderbird/3.1.10 MIME-Version: 1.0 To: Mel Gorman CC: Mel Gorman , linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Andrea Arcangeli , Benjamin Herrenschmidt , Rik van Riel , Johannes Weiner , KAMEZAWA Hiroyuki , linux-mm@kvack.org Subject: Re: [PATCH 2/3] mm: make the threshold of enabling THP configurable References: <1308587683-2555-1-git-send-email-amwang@redhat.com> <1308587683-2555-2-git-send-email-amwang@redhat.com> <20110620165955.GB9396@suse.de> <4DFF8050.9070201@redhat.com> <20110621093640.GD9396@suse.de> <4E015672.2020407@redhat.com> <20110622091611.GB7585@csn.ul.ie> <4E01C80F.8070605@redhat.com> <20110622111525.GK9396@suse.de> In-Reply-To: <20110622111525.GK9396@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1485 Lines: 33 于 2011年06月22日 19:15, Mel Gorman 写道: > On Wed, Jun 22, 2011 at 06:46:39PM +0800, Cong Wang wrote: >> ??? 2011???06???22??? 17:16, Mel Gorman ??????: >>> >>> What I meant was that there is a rational reason why 512M is the >>> default for enabling THP by default. Tuning it lower than that by any >>> means makes very little sense. Tuning it higher might make some sense >>> but it is more likely that THP would simply be disabled via sysctl. I >>> see very little advantage to introducing this Kconfig option other >>> than as a source of confusion when running make oldconfig. >>> >> >> The tunable range is (512, 8192), so 512M is the minimum. >> >> Sure, I knew it can be disabled via /sys, actually we can do even >> more in user-space, that is totally move the 512M check out of kernel, >> why we didn't? >> > > Because the reason why 512M is the default is not obvious and there > was no guarantee all distros would chose a reasonable default for > an init script (or know that an init script was even necessary). > This is one of the few cases where there is a sensible default that > is the least surprising. > Putting a well-explained Kconfig help would solve this problem, so I don't think this is a surprising thing. -- 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/