From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with SMTP id C5DF09000BD for ; Mon, 20 Jun 2011 13:01:25 -0400 (EDT) Message-ID: <4DFF7CDD.308@redhat.com> Date: Tue, 21 Jun 2011 01:01:17 +0800 From: Cong Wang MIME-Version: 1.0 Subject: Re: [PATCH 1/3] mm: completely disable THP by transparent_hugepage=never References: <1308587683-2555-1-git-send-email-amwang@redhat.com> <20110620165035.GE20843@redhat.com> In-Reply-To: <20110620165035.GE20843@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrea Arcangeli Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, Rik van Riel , Johannes Weiner , KAMEZAWA Hiroyuki , linux-mm@kvack.org ao? 2011a1'06ae??21ae?JPY 00:50, Andrea Arcangeli a??e??: > On Tue, Jun 21, 2011 at 12:34:28AM +0800, Amerigo Wang wrote: >> transparent_hugepage=never should mean to disable THP completely, >> otherwise we don't have a way to disable THP completely. >> The design is broken. > > We want to allow people to boot with transparent_hugepage=never but to > still allow people to enable it later at runtime. Not sure why you > find it broken... Your patch is just crippling down the feature with > no gain. There is absolutely no gain to disallow root to enable THP > later at runtime with sysfs, root can enable it anyway by writing into > /dev/mem. What can I do if I don't want to see THP at all? I mean the same behavior as when my CPU doesn't have PSE. With this patch, there is no even /sys/kernel/vm/transparent_hugepage/ exists. > > Unless you're root and you enable it, it's completely disabled, so I > don't see what you mean it's not completely disabled. Not even > khugepaged is started, try to grep of khugepaged... (that wouldn't be > the same with ksm where ksm daemon runs even when it's off for no > gain, but I explicitly solved the locking so khugepaged will go away > when enabled=never and return when enabled=always). Without this patch, THP is still initialized (although khugepaged is not started), that is what I don't want to see when I pass "transparent_hugepage=never", because "never" for me means THP is totally unseen, even not initialized. Thanks. -- 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 internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org