linux-kernel - Re: Question with maxcpus= parameter.

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Date:	Mon, 9 Nov 2015 13:47:20 +0800
From:	Zhenzhong Duan <zhenzhong.duan@...cle.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	rusty@...tcorp.com.au, ashok.raj@...el.com,
	LKML <linux-kernel@...r.kernel.org>,
	Feng Jin <joe.jin@...cle.com>
Subject: Re: Question with maxcpus= parameter.

Tried nr_cpus=4, works.

[root@...sq01 ~]# cat /sys/devices/system/cpu/possible
0-3
[root@...sq01 ~]# cat /sys/devices/system/cpu/present
0-3
[root@...sq01 ~]# uname -a
Linux rwssq01.us.oracle.com 3.8.13-44.1.1.el6uek.x86_64 #2 SMP Wed Sep 
10 06:10:25 PDT 2014 x86_64 x86_64 x86_64 GNU/Linux

zduan
在 2015/11/7 0:14, Konrad Rzeszutek Wilk 写道:
> On Fri, Nov 06, 2015 at 01:24:16PM +0800, Zhenzhong Duan wrote:
>> Hi Maintainers,
>>
>> Recently we faced an cpu online issue with maxcpus= parameter.
> Did you try 'nr_cpus' ?
>> We want to have 4 cpus onlined at bootup, test 3.8.13-stable on an 72 cpus
>> env with maxcpus=4, I found more cpus than 4 are onlined.
>> It's the udev scripts make them onlined. But below script exist for a long
>> time.
>> ACTION=="add", KERNEL=="cpu[0-9]*", RUN+="/bin/bash -c 'echo 1 >
>> /sys/devices/system/cpu/%k/online'"
>>
>> maxcpu= parameter didn't take effect, so is this a kernel bug? Or that
>> script should be removed?
>>
>> Btw: 2.6.39 works fine, I checked udev log, seems CPU ADD event is only sent
>> for 4cpus.
>> Why the difference between 2.6.39 and 3.8.13?
>>
>> thanks
>> zduan

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