From: Michael Ellerman <mpe@ellerman.id.au>
To: "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>,
Aravinda Prasad <aravinda@linux.vnet.ibm.com>,
Nathan Lynch <nathanl@linux.ibm.com>
Cc: linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2] powerpc/pseries: Fix maximum memory value
Date: Thu, 04 Jul 2019 21:13:26 +1000 [thread overview]
Message-ID: <871rz6qch5.fsf@concordia.ellerman.id.au> (raw)
In-Reply-To: <1561743225.hrre8pgw6j.naveen@linux.ibm.com>
"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> writes:
> Nathan Lynch wrote:
>> Aravinda Prasad <aravinda@linux.vnet.ibm.com> writes:
>>> Calculating the maximum memory based on the number of lmbs
>>> and lmb size does not account for the RMA region. Hence
>>> use memory_hotplug_max(), which already accounts for the
>>> RMA region, to fetch the maximum memory value. Thanks to
>>> Nathan Lynch for suggesting the memory_hotplug_max()
>>> function.
>>
>> Well, I hope I haven't led you astray... will it give you the desired
>> result on a kernel configured without memory hotplug support, booted in
>> an LPAR with some huge pages configured?
>>
>> If so, then
>> Acked-by: Nathan Lynch <nathanl@linux.ibm.com>
>>
>> It would likely help with review and future maintenance if the semantics
>> and intended use of the MaxMem field are made a little more
>> explicit. For example, is it supposed to include persistent memory?
>> Perhaps a follow-up patch could address this. Or maybe I'm overthinking
>> it.
>
> This was primarily aimed to replicate what AIX lparstat does and
> documentation (*) just says:
>
> Maximum Memory
> Maximum possible amount of Memory.
>
> I think this mirrors the maximum memory value set in the LPAR profile,
> and this provides a way to obtain that value from within the LPAR.
But the doc string for memory_hotplug_max() says:
* memory_hotplug_max - return max address of memory that may be added
ie. maximum *address* not maximum *amount*.
Possibly it turns out to be the same value, but that is just because you
have no holes in your layout.
So I don't think this patch is correct.
cheers
next prev parent reply other threads:[~2019-07-04 11:15 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-28 6:53 [PATCH v2] powerpc/pseries: Fix maximum memory value Aravinda Prasad
2019-06-28 17:27 ` Nathan Lynch
2019-06-28 17:38 ` Naveen N. Rao
2019-06-28 18:19 ` Nathan Lynch
2019-07-04 11:13 ` Michael Ellerman [this message]
2019-07-04 11:30 ` Aravinda Prasad
2019-07-01 4:03 ` Aravinda Prasad
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