Re: Question with maxcpus= parameter.

From: Zhenzhong Duan
Date: Mon Nov 09 2015 - 00:48:06 EST


Tried nr_cpus=4, works.

[root@rwssq01 ~]# cat /sys/devices/system/cpu/possible
0-3
[root@rwssq01 ~]# cat /sys/devices/system/cpu/present
0-3
[root@rwssq01 ~]# 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
å 2015/11/7 0:14, Konrad Rzeszutek Wilk åé:
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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