>>> On Wed, Nov 7, 2007 at 11:38 AM, in message <[EMAIL PROTECTED]>, Mark Perry <[EMAIL PROTECTED]> wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA1 > > Mary Anne Matyaz wrote: >> Can you add a CPU while it's running? From the linux side, I mean? >> We couldn't figure out how to get linux to recognize a new cpu. >> Mary Anne >> > Yes > > But ensure that Linux is capable of handling more CPUs at boot time. > (maxcpu=n)
Actually, the needed parameter is either "additional_cpus=#" or "possible_cpus=#". The additional_cpus parameter will cause the kernel to reserve "#" more slots for CPUs than were detected at boot time. The "possible_cpus" parameter will cause the kernel to create exactly "#" slots for CPUs, no matter how many were detected at boot time, even if the number is smaller than the number of CPUs that were detected. Specifying possible_cpus will cause any additional_cpus parameter to be ignored. The maxcpus (note the s on the end) parameter tells the kernel to only _start_ "#" number of CPUs, even if more were detected at boot time. If there were more defined, you can bring the others online later (see below). If fewer CPUs were detected, maxcpus has no real effect. If an additional CPU gets DEFINEd (via CP), or configured online (in an LPAR), you then need to bring it online to the Linux system by echoing a "1" into /sys/devices/system/cpu/cpu?/online, where ? equals the number of the CPU, (starting with 0). Whew! Mark Post ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
