linux-kernel - Re: [PATCH 1/3] mm: completely disable THP by transparent

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Message-ID: <4DFF7F0A.8090604@redhat.com>
Date:	Mon, 20 Jun 2011 13:10:34 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Cong Wang <amwang@...hat.com>
CC:	Mel Gorman <mgorman@...e.de>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <jweiner@...hat.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	linux-mm@...ck.org
Subject: Re: [PATCH 1/3] mm: completely disable THP by transparent_hugepage=never

On 06/20/2011 01:07 PM, Cong Wang wrote:
> 于 2011年06月21日 00:58, Mel Gorman 写道:
>> 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.
>>>
>>
>> I don't get why it's broken. Why would the user be prevented from
>> enabling it at runtime?
>>
>
> We need to a way to totally disable it, right? Otherwise, when I configure
> THP in .config, I always have THP initialized even when I pass "=never".
>
> For me, if you don't provide such way to disable it, it is not flexible.
>
> I meet this problem when I try to disable THP in kdump kernel, there is
> no user of THP in kdump kernel, THP is a waste for kdump kernel. This is
> why I need to find a way to totally disable it.

What you have not explained yet is why having THP
halfway initialized (but not used, and without a
khugepaged thread) is a problem at all.

Why is it a problem for you?
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