linux-kernel - Re: FW: Linux question

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Date:	Fri, 07 Mar 2008 13:43:45 -0500
From:	Bill Davidsen <davidsen@....com>
To:	Justin Banks <justinb@...bone.com>
CC:	"Miller, Mike (OS Dev)" <Mike.Miller@...com>,
	linux-kernel@...r.kernel.org
Subject: Re: FW: Linux question

Justin Banks wrote:
> Miller, Mike (OS Dev) wrote
>> Is there a way in to limit the kernel to seeing only the cores on a
>> single processor and ignore all other processor cores (eg. leave
>> them in HALT)?
> 
> Can't you just echo 0 into /sys/devices/system/cpu/cpuN/online where the
> /sys/devices/system/cpu/cpuN/topology/physical_package_id isn't the one
> you want to keep online?
> 
Here's an interesting question, why isn't there an "online" file for 
each CPU?

Example:

posidon:davidsen> l /sys/devices/system/cpu/cpu?
/sys/devices/system/cpu/cpu0:
total 0
drwxr-xr-x 5 root    0 Feb  7 12:57 cache
drwxr-xr-x 3 root    0 Mar  7 13:28 cpufreq
-r-------- 1 root 4096 Mar  7 13:28 crash_notes
drwxr-xr-x 2 root    0 Mar  7 13:28 microcode
drwxr-xr-x 2 root    0 Mar  7 13:28 topology

/sys/devices/system/cpu/cpu1:
total 0
drwxr-xr-x 5 root    0 Feb  7 12:57 cache
drwxr-xr-x 3 root    0 Mar  7 13:28 cpufreq
-r-------- 1 root 4096 Mar  7 13:28 crash_notes
drwxr-xr-x 2 root    0 Mar  7 13:28 microcode
-rw-r--r-- 1 root 4096 Mar  7 13:28 online
drwxr-xr-x 2 root    0 Mar  7 13:28 topology


-- 
Bill Davidsen <davidsen@....com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot
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