Message-ID: <52419F63.6010504@gmail.com>
Date: Tue, 24 Sep 2013 22:19:15 +0800
From: Zhang Yanfei <zhangyanfei.yes@gmail.com>
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To: Tejun Heo <tj@kernel.org>
CC: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>,
        "Rafael J . Wysocki" <rjw@sisk.pl>, lenb@kernel.org,
        Thomas Gleixner <tglx@linutronix.de>, mingo@elte.hu,
        "H. Peter Anvin" <hpa@zytor.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Toshi Kani <toshi.kani@hp.com>, Wanpeng Li <liwanp@linux.vnet.ibm.com>,
        Thomas Renninger <trenn@suse.de>, Yinghai Lu <yinghai@kernel.org>,
        Jiang Liu <jiang.liu@huawei.com>, Wen Congyang <wency@cn.fujitsu.com>,
        Lai Jiangshan <laijs@cn.fujitsu.com>, isimatu.yasuaki@jp.fujitsu.com,
        izumi.taku@jp.fujitsu.com, Mel Gorman <mgorman@suse.de>,
        Minchan Kim <minchan@kernel.org>, mina86@mina86.com,
        gong.chen@linux.intel.com, vasilis.liaskovitis@profitbricks.com,
        lwoodman@redhat.com, Rik van Riel <riel@redhat.com>,
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        "x86@kernel.org" <x86@kernel.org>, linux-doc@vger.kernel.org,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Linux MM <linux-mm@kvack.org>, linux-acpi@vger.kernel.org,
        imtangchen@gmail.com
Subject: Re: [PATCH 2/6] memblock: Introduce bottom-up allocation mode
References: <524162DA.30004@cn.fujitsu.com> <524163CF.3010303@cn.fujitsu.com> <20130924121725.GC2366@htj.dyndns.org> <524190DC.4060605@gmail.com> <20130924132327.GH2366@htj.dyndns.org> <52419DC6.4030800@gmail.com> <20130924141640.GK2366@htj.dyndns.org>
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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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