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

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Message-ID: <20151106065755.GA62424@otc-brkl-03.jf.intel.com>
Date:	Fri, 6 Nov 2015 01:57:56 -0500
From:	"Raj, Ashok" <ashok.raj@...el.com>
To:	Zhenzhong Duan <zhenzhong.duan@...cle.com>
Cc:	rusty@...tcorp.com.au, LKML <linux-kernel@...r.kernel.org>,
	Feng Jin <joe.jin@...cle.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Ashok Raj <ashok.raj@...el.com>
Subject: Re: Question with maxcpus= parameter.

Hi Zduan

do you know which distribution it is? This isn't a kernel bug.

if you look at dmesg you should see how many CPUs were booted. But the sysfs
files are created and the usermode script is bringing every cpu online.

Tony mentioned this to me couple weeks ago when i was fixing another bug
in maxcpus. I think you can safely remove the script and it should be fine.

Cheers,
Ashok


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.
> 
> 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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