Messages in this thread | | | Date | Tue, 21 Feb 2006 21:24:15 +0100 | From | Martin Peschke <> | Subject | How to allocate per-cpu data for online CPUs only (and safely)? |
| |
I am trying to optimize the memory footprint of some code of mine. It's been using per-cpu data and alloc_percpu() so far. The latter has the disadvantage of getting hold of memory for CPU's which aren't there (yet).
I could imagine using CPU-hotplug notifications as triggers for additional allocations or for cleaning up unneeded memory. But alloc_percpu() appears to conflict with that idea.
I was briefly tempted to derive some code from alloc_percpu() more to my liking, until I was scared off by this comment in alloc_percpu():
/* * Cannot use for_each_online_cpu since a cpu may come online * and we have no way of figuring out how to fix the array * that we have allocated then.... */
Well, and then there is kernel/profile.c, for example, which boldly ignors alloc_percpu()'s qualms and allocates and releases per-cpu data as needed.
Is that the way to go? If so, why alloc_percpu()'s reservations? Or, does that comment imply that the exploiter isn't expected to take care of CPU hotplug events? Am I missing anything?
Thank you.
Martin
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |