linux-kernel - Re: [PATCH 0/3] memblock related top down

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Date:	Tue, 28 Dec 2010 14:25:06 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>
Subject: Re: [PATCH 0/3] memblock related top down

On Tue, Dec 28, 2010 at 2:09 PM, H. Peter Anvin <hpa@...or.com> wrote:
> On 12/28/2010 01:36 PM, Yinghai Lu wrote:
>> On Tue, Dec 28, 2010 at 12:21 PM, H. Peter Anvin <hpa@...or.com> wrote:
>>> On 12/17/2010 04:58 PM, Yinghai Lu wrote:
>>>> Please check
>>>>
>>>> Those three patches to make memblock allocation more top to down.
>>>>
>>>
>>> Please explain what you mean with "more top to down".  Not what the code
>>> does, but what is the goal of the patchset.
>>
>> for example first node with 16g ram, it is into two parts: [0, 2g),
>> and [4g, 18g).
>>
>> alloc_bootmem will get allocation from [0, 2g) always until we have
>> can not find more.
>>
>> with third patch, it will try to get from [4g, 18g) at first.
>>
>> second patch is need to applied before third patch, because old way
>> happenly get under 4g for generic bootmem under 4g
>>
>> First one is trying not to put page table for [0, 4g) under 512M.
>>
>
> The goal of this is to free up low memory for DMA and kdump, I presume?

yes.  otherwise if we put pgtable around 512M, then we have no chance
to allocate 512M for kdump under 896M.
if we put pgtable near 2g <assume [2g, 4g) for mmio),  We can make it happen.

later 6 patches will put try to pgtable on local node.

Thanks
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