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

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Date:	Wed, 14 Oct 2015 11:28:57 +0800
From:	Xishi Qiu <qiuxishi@...wei.com>
To:	Tang Chen <tangchen@...fujitsu.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>
Subject: Re: [PATCH] mm: skip if required_kernelcore is larger than totalpages

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.

Thanks,
Xishi Qiu

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