Hi,<br><br>I need to know the difference between making a cpu logically offline <br>and physically offline. I have read that the following command <br><br>$ echo 0  &gt; /sys/device/system/cpu/&lt;cpu number&gt;/online<br>
<br>makes a cpu logically offline. It frees the cpu from interrupts and migrates running processes.<br>But then what does it mean to make a cpu physically offline ?<br>I referred to following article :<br><br><a href="http://www.kernel.org/doc/Documentation/cpu-hotplug.txt">http://www.kernel.org/doc/Documentation/cpu-hotplug.txt</a><br>
<br>Here is the relevant excerpt :<br><br><span class="Apple-style-span" style="color: rgb(0, 0, 0); font-family: &#39;Times New Roman&#39;; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><pre style="word-wrap: break-word; white-space: pre-wrap; ">
Q: Does hot-add/hot-remove refer to physical add/remove of cpus?
A: The usage of hot-add/remove may not be very consistently used in the code.
CONFIG_HOTPLUG_CPU enables logical online/offline capability in the kernel.
To support physical addition/removal, one would need some BIOS hooks and
the platform should have something like an attention button in PCI hotplug.
CONFIG_ACPI_HOTPLUG_CPU enables ACPI support for physical add/remove of CPUs.</pre></span><br><br>Please help!<br><br>Thanks<br>Vaibhav Jain<br>