On Wed, Aug 17, 2011 at 9:14 AM, Vaibhav Jain <vjoss197@xxxxxxxxx> wrote: > Hi, > > I need to know the difference between making a cpu logically offline > and physically offline. I have read that the following command > > $ echo 0 > /sys/device/system/cpu/<cpu number>/online > > makes a cpu logically offline. It frees the cpu from interrupts and migrates > running processes. > But then what does it mean to make a cpu physically offline ? > I referred to following article : > > http://www.kernel.org/doc/Documentation/cpu-hotplug.txt > > Here is the relevant excerpt : > > 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. > > Please help! > > Thanks > Vaibhav Jain > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@xxxxxxxxxxxxxxxxx > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies > > Hi Vaibhav! I think physical CPU hot-plug is a capability to plug in and out processing device (CPU) on running machine. Logical CPU hot-plug is a capability to add on and remove out already available processing units (CPU s or cores) under SMP domain of OS. P.S. Sorry for my weak English. _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
