linux-kernel - Re: [PATCH v2 0/5] Add movablecore

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Message-ID: <50B73B22.90500@jp.fujitsu.com>
Date:	Thu, 29 Nov 2012 19:38:26 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	"Luck, Tony" <tony.luck@...el.com>
CC:	Jiang Liu <jiang.liu@...wei.com>,
	Tang Chen <tangchen@...fujitsu.com>,
	"hpa@...or.com" <hpa@...or.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"rob@...dley.net" <rob@...dley.net>,
	"laijs@...fujitsu.com" <laijs@...fujitsu.com>,
	"wency@...fujitsu.com" <wency@...fujitsu.com>,
	"linfeng@...fujitsu.com" <linfeng@...fujitsu.com>,
	"yinghai@...nel.org" <yinghai@...nel.org>,
	"kosaki.motohiro@...fujitsu.com" <kosaki.motohiro@...fujitsu.com>,
	"minchan.kim@...il.com" <minchan.kim@...il.com>,
	"mgorman@...e.de" <mgorman@...e.de>,
	"rientjes@...gle.com" <rientjes@...gle.com>,
	"rusty@...tcorp.com.au" <rusty@...tcorp.com.au>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	Len Brown <lenb@...nel.org>,
	"Wang, Frank" <frank.wang@...el.com>
Subject: Re: [PATCH v2 0/5] Add movablecore_map boot option

Hi Tony,

2012/11/29 6:34, Luck, Tony wrote:
>> 1. use firmware information
>>    According to ACPI spec 5.0, SRAT table has memory affinity structure
>>    and the structure has Hot Pluggable Filed. See "5.2.16.2 Memory
>>    Affinity Structure". If we use the information, we might be able to
>>    specify movable memory by firmware. For example, if Hot Pluggable
>>    Filed is enabled, Linux sets the memory as movable memory.
>>
>> 2. use boot option
>>    This is our proposal. New boot option can specify memory range to use
>>    as movable memory.
>
> Isn't this just moving the work to the user? To pick good values for the

Yes.

> movable areas, they need to know how the memory lines up across
> node boundaries ... because they need to make sure to allow some
> non-movable memory allocations on each node so that the kernel can
> take advantage of node locality.

There is no problem.
Linux has already two boot options, kernelcore= and movablecore=.
So if we use them, non-movable memory is divided into each node evenly.

But there is no way to specify a node used as movable currently. So
we proposed the new boot option.

> So the user would have to read at least the SRAT table, and perhaps
> more, to figure out what to provide as arguments.
>

> Since this is going to be used on a dynamic system where nodes might
> be added an removed - the right values for these arguments might
> change from one boot to the next. So even if the user gets them right
> on day 1, a month later when a new node has been added, or a broken
> node removed the values would be stale.

I don't think so. Even if we hot add/remove node, the memory range of
each memory device is not changed. So we don't need to change the boot
option.

Thanks,
Yasuaki Ishimatsu

>
> -Tony
>


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