linux-kernel - Re: [PATCH 2/6] memblock: Introduce bottom-up allocation mode

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Date:	Tue, 24 Sep 2013 22:19:15 +0800
From:	Zhang Yanfei <zhangyanfei.yes@...il.com>
To:	Tejun Heo <tj@...nel.org>
CC:	Zhang Yanfei <zhangyanfei@...fujitsu.com>,
	"Rafael J . Wysocki" <rjw@...k.pl>, lenb@...nel.org,
	Thomas Gleixner <tglx@...utronix.de>, mingo@...e.hu,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Toshi Kani <toshi.kani@...com>,
	Wanpeng Li <liwanp@...ux.vnet.ibm.com>,
	Thomas Renninger <trenn@...e.de>,
	Yinghai Lu <yinghai@...nel.org>,
	Jiang Liu <jiang.liu@...wei.com>,
	Wen Congyang <wency@...fujitsu.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	isimatu.yasuaki@...fujitsu.com, izumi.taku@...fujitsu.com,
	Mel Gorman <mgorman@...e.de>, Minchan Kim <minchan@...nel.org>,
	mina86@...a86.com, gong.chen@...ux.intel.com,
	vasilis.liaskovitis@...fitbricks.com, lwoodman@...hat.com,
	Rik van Riel <riel@...hat.com>, jweiner@...hat.com,
	prarit@...hat.com, "x86@...nel.org" <x86@...nel.org>,
	linux-doc@...r.kernel.org,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux MM <linux-mm@...ck.org>, linux-acpi@...r.kernel.org,
	imtangchen@...il.com
Subject: Re: [PATCH 2/6] memblock: Introduce bottom-up allocation mode

On 09/24/2013 10:16 PM, Tejun Heo wrote:
> Hello,
> 
> On Tue, Sep 24, 2013 at 10:12:22PM +0800, Zhang Yanfei wrote:
>> I see. I think it is rarely to fail. But here is case that it must
>> fail in the current bottom-up implementation. For example, we allocate
>> memory in reserve_real_mode() by calling this: 
>> memblock_find_in_range(0, 1<<20, size, PAGE_SIZE);
>>
>> Both the start and end is below the kernel, so trying bottom-up for
>> this must fail. So I am now thinking that if we should take this as
>> the special case for bottom-up. That said, if we limit start and end
>> both below the kernel, we should allocate memory below the kernel instead
>> of make it fail. The cases are also rare, in early boot time, only
>> these two:
>>
>>  |->early_reserve_e820_mpc_new()   /* allocate memory under 1MB */
>>  |->reserve_real_mode()            /* allocate memory under 1MB */
>>
>> How do you think?
> 
> They need to be special cased regardless, right?  It's wrong to print
> out warning messages for things which are expected to behave that way.
> Just skip bottom-up allocs if @end is under kernel image?
> 

Good idea. Will do this way.

-- 
Thanks.
Zhang Yanfei
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