linux-kernel - Re: sched: CPU #1's llc-sibling CPU #0 is not on the same node!

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Date:	Wed, 27 Feb 2013 14:49:29 +0900
From:	Yasuaki Ishimatsu <isimatu.yasuaki@...fujitsu.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Tang Chen <tangchen@...fujitsu.com>,
	Don Morris <don.morris@...com>,
	Tim Gardner <tim.gardner@...onical.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Tejun Heo <tj@...nel.org>, Tony Luck <tony.luck@...el.com>,
	Thomas Renninger <trenn@...e.de>,
	<linux-kernel@...r.kernel.org>, <tglx@...utronix.de>,
	<mingo@...hat.com>, <a.p.zijlstra@...llo.nl>,
	<jarkko.sakkinen@...el.com>
Subject: Re: sched: CPU #1's llc-sibling CPU #0 is not on the same node!

2013/02/27 14:11, Yinghai Lu wrote:
> On Tue, Feb 26, 2013 at 8:43 PM, Yasuaki Ishimatsu
> <isimatu.yasuaki@...fujitsu.com> wrote:
>> 2013/02/27 13:04, Yinghai Lu wrote:
>>>
>>> On Tue, Feb 26, 2013 at 7:38 PM, Yasuaki Ishimatsu
>>> <isimatu.yasuaki@...fujitsu.com> wrote:
>>>>
>>>> 2013/02/27 11:30, Yinghai Lu wrote:
>>>>>
>>>>> Do you mean you can not boot one socket system with 1G ram ?
>>>>> Assume socket 0 does not support hotplug, other 31 sockets support hot
>>>>> plug.
>>>>>
>>>>> So we could boot system only with socket0, and later one by one hot
>>>>> add other cpus.
>>>>
>>>>
>>>>
>>>> In this case, system can boot. But other cpus with bunch of ram hot
>>>> plug may fails, since system does not have enough memory for cover
>>>> hot added memory. When hot adding memory device, kernel object for the
>>>> memory is allocated from 1G ram since hot added memory has not been
>>>> enabled.
>>>>
>>>
>>> yes, it may fail, if the one node memory need page table and vmemmap
>>> is more than 1g ...
>>>
>>

>>> for hot add memory we need to
>>> 1. add another wrapper for init_memory_mapping, just like
>>> init_mem_mapping() for booting path.
>>> 2. we need make memblock more generic, so we can use it with hot add
>>> memory during runtime.
>>> 3. with that we can initialize page table for hot added node with ram.
>>> a. initial page table for 2M near node top is from node0 ( that does
>>> not support hot plug).
>>> b. then will use 2M for memory below node top...
>>> c. with that we will make sure page table stay on local node.
>>>    alloc_low_pages need to be updated to support that.
>>> 4. need to make sure vmemmap on local node too.
>>
>>
>> I think so too. By this, memory hot plug becomes more useful.

I agree with your idea. But I think above ideas is future work.
So at first we should use movable memory for memory hot plug.
After that, we will implement above ideas.

>>
>>>
>>> so hot-remove node will work too later.
>>>
>>> In the long run, we should make booting path and hot adding more
>>> similar and share at most code.
>>> That will make code get more test coverage.
>
> Tang,  Yasuaki, Andrew,
>
> Please check if you are ok with attached reverting patch.

We will fix this problem with no objection. So please wait a while.

And the problem occurs by "movablemem_map=srat" not "movablemem_map=nn[KMG]@ss[KMG]"
At least, if you want to revert it, you should revert only "movablemem_map=srat" part.

Thanks,
Yasuaki Ishimatsu  

>
> Tim, Don,
> Can you try if attached reverting patch fix all the problems for you ?
>
> Thanks
>
> Yinghai
>


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