linux-kernel - Re: [PATCH] mm: skip if required_kernelcore is larger than totalpages

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Message-ID: <561DD40B.5060509@cn.fujitsu.com>
Date:	Wed, 14 Oct 2015 12:03:23 +0800
From:	Tang Chen <tangchen@...fujitsu.com>
To:	Xishi Qiu <qiuxishi@...wei.com>
CC:	Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>,
	David Rientjes <rientjes@...gle.com>, <zhongjiang@...wei.com>,
	Linux MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>, <tangchen@...fujitsu.com>
Subject: Re: [PATCH] mm: skip if required_kernelcore is larger than totalpages


On 10/14/2015 11:28 AM, Xishi Qiu wrote:
> On 2015/10/14 10:50, Tang Chen wrote:
>
>> Hi, Qiu
>>
>> The patch seems OK to me. Only one little concern below.
>>
>> On 10/12/2015 09:37 AM, Xishi Qiu wrote:
>>> On 2015/10/9 23:41, Yasuaki Ishimatsu wrote:
>>>
>>>> On Thu, 8 Oct 2015 10:21:05 +0800
>>>> Xishi Qiu <qiuxishi@...wei.com> wrote:
>>>>
>>>>> If kernelcore was not specified, or the kernelcore size is zero
>>>>> (required_movablecore >= totalpages), or the kernelcore size is larger
>>>> Why does required_movablecore become larger than totalpages, when the
>>>> kernelcore size is zero? I read the code but I could not find that you
>>>> mention.
>>>>
>>> If user only set boot option movablecore, and the value is larger than
>>> totalpages, the calculation of kernelcore is zero, but we can't fill
>>> the zone only with kernelcore, so skip it.
>>>
>>> I have send a patch before this patch.
>>> "fix overflow in find_zone_movable_pfns_for_nodes()"
>>>          ...
>>>            required_movablecore =
>>>                roundup(required_movablecore, MAX_ORDER_NR_PAGES);
>>> +        required_movablecore = min(totalpages, required_movablecore);
>>>            corepages = totalpages - required_movablecore;
>>>          ...
>>
>> So if required_movablecore >= totalpages, there won't be any ZONE_MOVABLE.
>> How about add a warning or debug info to tell the user he has specified a
>> too large movablecore, and it is ignored ?
>>
>> Thanks.
> Yes, but I don't think is is necessary, user should know the total memory
> before he set the boot option.

Well, I'm just thinking if I set a too large movablecore, but I didn't 
realize it.
And when the system boots up, there is no ZONE_MOVABLE. It may confuse me.

Thanks.

>
> Thanks,
> Xishi Qiu
>
> .
>

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