On Thu, 18 Feb 2010, H. Peter Anvin wrote: > > per_cpu setup will allocate some mem for every cpu according to possible cpus. > > > > Yes, and I have repeatedly requested that we allocate the memory on the > first up of a disabled CPU rather than eagerly, but in *most* > configurations the amount is relatively small. The size of the static per cpu segment is likely around 30k and you will likely add another 30k in dynamic allocations. As I have also repeatedly stated: Dynamic percpu data allocation when onlining / offlining processors will complicate locking (cannot rely on percpu be present anymore) and introduce numerous additional hotplug notifiers into subsystems. Newly allocating a per cpu segment also has consequences for subsystems that dynamically allocate per cpu data (not add another cpu but dynamically allocate data that needs to be present on all processors). They would have to prepare the per cpu data which would create another need for callbacks. All of the measures necessary would result in problems of ensuring object existence in critical code paths that use percpu data for performance reasons. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
