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From: Balbir Singh <bsingharora@gmail.com>
Date: Wed, 14 Jun 2017 15:27:26 +1000
Message-ID: <CAKTCnzm7jB1doPjySSjBe6B6YhTOkU+Cm+DJA94PQ7rNyXpx4Q@mail.gmail.com>
Subject: Re: RESEND Re: [Patch 2/2]: powerpc/hotplug/mm: Fix hot-add memory
 node assoc
To: Michael Bringmann <mwb@linux.vnet.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>,
        Reza Arbab <arbab@linux.vnet.ibm.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Paul Mackerras <paulus@samba.org>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
        Bharata B Rao <bharata@linux.vnet.ibm.com>,
        Shailendra Singh <shailendras@nvidia.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        "open list:LINUX FOR POWERPC (32-BIT AND 64-BIT)" 
        <linuxppc-dev@lists.ozlabs.org>,
        Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
        Michael Bringmann from Kernel Team <mbringm@us.ibm.com>
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Sender: linux-kernel-owner@vger.kernel.org
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On Wed, Jun 14, 2017 at 3:25 PM, Balbir Singh <bsingharora@gmail.com> wrote:
>
>
> On Wed, Jun 14, 2017 at 8:21 AM, Michael Bringmann <mwb@linux.vnet.ibm.com>
> wrote:
>>
>> On a related note, we are discussing the addition of 2 new device-tree
>> properties
>> with Pete Heyrman and his fellows that should simplify the determination
>> of the
>> set of required nodes.
>>
>> * One property would provide the total/max number of nodes needed by the
>> kernel
>>   on the current hardware.
>
>

Yes, that would be nice to have

>
>>
>> * A second property would provide the total/max number of nodes that the
>> kernel
>>   could use on any system to which it could be migrated.
>>
>

Not sure about this one, are you suggesting more memory can be added
depending on the migration target?

>
>
>>
>> These properties aren't available, yet, and it takes time to define new
>> properties
>> in the PAPR and have them implemented in pHyp and the kernel.  As an
>> intermediary
>> step, the systems which are doing a lot of dynamic hot-add/hot-remove
>> configuration
>> could provide equivalent information to the PowerPC kernel with a command
>> line
>> parameter.  The 'numa.c' code would then read this value and fill in the
>> necessary
>> entries in the 'node_possible_map'.
>>
>> Would you foresee any problems with using such a feature?
>
>

Sorry my mailer goofed up, resending

Balbir Singh