linux-kernel - Re: [PATCH v3 2/5] memblock: Improve memblock to support allocation from lower address.

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Message-ID: <5240FBEF.10102@cn.fujitsu.com>
Date:	Tue, 24 Sep 2013 10:41:51 +0800
From:	Zhang Yanfei <zhangyanfei@...fujitsu.com>
To:	Tejun Heo <tj@...nel.org>
CC:	Zhang Yanfei <zhangyanfei.yes@...il.com>,
	Tang Chen <tangchen@...fujitsu.com>, rjw@...k.pl,
	lenb@...nel.org, tglx@...utronix.de, mingo@...e.hu, hpa@...or.com,
	akpm@...ux-foundation.org, toshi.kani@...com,
	liwanp@...ux.vnet.ibm.com, trenn@...e.de, yinghai@...nel.org,
	jiang.liu@...wei.com, wency@...fujitsu.com, laijs@...fujitsu.com,
	isimatu.yasuaki@...fujitsu.com, izumi.taku@...fujitsu.com,
	mgorman@...e.de, minchan@...nel.org, mina86@...a86.com,
	gong.chen@...ux.intel.com, vasilis.liaskovitis@...fitbricks.com,
	lwoodman@...hat.com, riel@...hat.com, jweiner@...hat.com,
	prarit@...hat.com, x86@...nel.org, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-acpi@...r.kernel.org
Subject: Re: [PATCH v3 2/5] memblock: Improve memblock to support allocation
 from lower address.

Hello tejun,

On 09/24/2013 04:21 AM, Tejun Heo wrote:
> Hello,
> 
> On Tue, Sep 24, 2013 at 02:07:13AM +0800, Zhang Yanfei wrote:
>> Yes, I am following your advice in principle but kind of confused by
>> something you said above. Where should the set_memblock_alloc_above_kernel
>> be used? IMO, the function is like:
>>
>> find_in_range_node()
>> {
>>      if (ok) {
>>            /* bottom-up */
>>            ret = __memblock_find_in_range(max(start, _end_of_kernel), end...);
>>            if (!ret)
>>                  return ret;
>>      }
>>
>>      /* top-down retry */
>>      return __memblock_find_in_range_rev(start, end...)
>> }
>>
>> For bottom-up allocation, we always start from max(start, _end_of_kernel).
> 
> Oh, I was talking about naming of the memblock_set_bottom_up()
> function.  We aren't really doing pure bottom up allocations, so I
> think it probably would be clearer if the name clearly denotes that
> we're doing above-kernel allocation.

I see. But I think memblock_set_alloc_above_kernel may lose the info
that we are doing bottom-up allocation. So my idea is we introduce
pure bottom-up allocation mode in previous patches and we use the
bottom-up allocation here and limit the start address above the kernel
, with explicit comments to indicate this.

How do you think?

Thanks.

> 
> Thanks.
> 


-- 
Thanks.
Zhang Yanfei
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