linux-kernel - Re: [PATCH part5 0/7] Arrange hotpluggable memory as ZONE

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Date:	Wed, 14 Aug 2013 16:29:05 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	Tejun Heo <tj@...nel.org>
CC:	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Tang Chen <imtangchen@...il.com>,
	Tang Chen <tangchen@...fujitsu.com>, robert.moore@...el.com,
	lv.zheng@...el.com, rjw@...k.pl, lenb@...nel.org,
	tglx@...utronix.de, mingo@...e.hu, hpa@...or.com,
	akpm@...ux-foundation.org, 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, zhangyanfei@...fujitsu.com,
	yanghy@...fujitsu.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 part5 0/7] Arrange hotpluggable memory as ZONE_MOVABLE.

(8/14/13 3:55 PM), Tejun Heo wrote:
> Hello,
>
> On Wed, Aug 14, 2013 at 03:40:31PM -0400, KOSAKI Motohiro wrote:
>> I don't agree it. Please look at other kernel options. A lot of these don't
>> follow you. These behave as direction, not advise.
>>
>> I mean the fallback should be implemented at turning on default the feature.
>
> Yeah, some options are "please try this" and others "do this or fail".
> There's no frigging fundamental rule there.

In this case, we have zero worth for fallback, right?


>> I don't read whole discussion and I don't quite understand why no kernel
>> place controlling is relevant. Every unpluggable node is suitable for
>> kernel. If you mean current kernel placement logic don't care plugging,
>> that's a bug.
>>
>> If we aim to hot remove, we have to have either kernel relocation or
>> hotplug awre kernel placement at boot time.
>
> What if all nodes are hot pluggable?  Are we moving the kernel
> dynamically then?

Intel folks already told, we have no such system in practice.


>>> Failing to boot is *way* worse reporting mechanism than almost
>>> everything else.  If the sysadmin is willing to risk machines failing
>>> to come up, she would definitely be willing to check whether which
>>> memory areas are actually hotpluggable too, right?
>>
>> No. see above. Your opinion is not pragmatic useful.
>
> No, what you're saying doesn't make any sense.  There are multiple
> ways to report when something doesn't work.  Failing to boot is *one*
> of them and not a very good one.  Here, for practical reasons, the end
> result may differ depending on the specifics of the configuration, so
> more detailed reporting is necessary anyway, so why do you insist on
> failing the boot?  In what world is it a good thing for the machine to
> fail boot after bios or kernel update?

Because boot failure have no chance to overlook and better way for practice.



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