Message-ID: <4DFF8106.8090702@redhat.com>
Date: Tue, 21 Jun 2011 01:19:02 +0800
From: Cong Wang <amwang@redhat.com>
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To: Rik van Riel <riel@redhat.com>
CC: Mel Gorman <mgorman@suse.de>, linux-kernel@vger.kernel.org,
        akpm@linux-foundation.org, Andrea Arcangeli <aarcange@redhat.com>,
        Johannes Weiner <jweiner@redhat.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, linux-mm@kvack.org
Subject: Re: [PATCH 1/3] mm: completely disable THP by transparent_hugepage=never
References: <1308587683-2555-1-git-send-email-amwang@redhat.com> <20110620165844.GA9396@suse.de> <4DFF7E3B.1040404@redhat.com> <4DFF7F0A.8090604@redhat.com>
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于 2011年06月21日 01:10, Rik van Riel 写道:
> 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?

It occupies some memory, memory is valuable in kdump kernel (usually
only 128M). :) Since I am sure no one will use it, why do I still need
to initialize it at all?

Thanks.
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