Hi Gautham- Gautham R Shenoy wrote: > > Looking at the topology_init() code, I observe that the meaning of > the cpuX/ directory entries in /sys/devices/system/cpu/ might be > different for different architectures. > > Looks like, in case of i386, ia64, m32, mips etc, the cpuX directory entries > represent the "present cpus". > > However, in case of powerpc, s390 etc, the cpuX entries represent the > "possible cpus". > > Wondering if there is any particular reason for this discrepancy.
I believe that the powerpc behavior was established before cpu_present_map was introduced. > I am not entirely surely if it's due cpu hotplug because > both i386 and powerpc support it! powerpc also supports processor add and remove (as opposed to online/offline); i386 does not AFAIK. I think this may be a reason for the difference. > When I do a > "echo 1 > /sys/devices/system/cpu/cpuX/online" on a power box as root, > I might get "-bash: echo: write error: Invalid argument" > because cpuX might not be present! > > In case of lpar, cpu_present_map need not necessarily be equal to > cpu_possible_map, so the above error is observable. Working as intended. You have to add a cpu to the partition before you can online it. > Is this discrepency intentional ? > Or is it due to the fact that in most cases, > cpu_present_map == cpu_possible_map, so lets not bother about it :-? I think it's the inevitable result when architectures are free to invent their own versions of the same sysfs interface. But is it really causing a problem in this case? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
