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Subject: Re: [PATCH part5 0/7] Arrange hotpluggable memory as ZONE_MOVABLE.
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Wed, 14 Aug 2013 13:30:38 -0700
To: KOSAKI Motohiro <kosaki.motohiro@gmail.com>, Tejun Heo <tj@kernel.org>
CC: Tang Chen <imtangchen@gmail.com>, Tang Chen <tangchen@cn.fujitsu.com>,
        robert.moore@intel.com, lv.zheng@intel.com, rjw@sisk.pl,
        lenb@kernel.org, tglx@linutronix.de, mingo@elte.hu,
        akpm@linux-foundation.org, trenn@suse.de, yinghai@kernel.org,
        jiang.liu@huawei.com, wency@cn.fujitsu.com, laijs@cn.fujitsu.com,
        isimatu.yasuaki@jp.fujitsu.com, izumi.taku@jp.fujitsu.com,
        mgorman@suse.de, minchan@kernel.org, mina86@mina86.com,
        gong.chen@linux.intel.com, vasilis.liaskovitis@profitbricks.com,
        lwoodman@redhat.com, riel@redhat.com, jweiner@redhat.com,
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        linux-acpi@vger.kernel.org
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There are systems which can.  They have the ability to remap in hardware.

KOSAKI Motohiro <kosaki.motohiro@gmail.com> wrote:
>(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.

-- 
Sent from my mobile phone. Please excuse brevity and lack of formatting.
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