On Mon, Jul 13, 2015 at 7:01 AM, Christoph Lameter <c...@linux.com> wrote: > On Mon, 13 Jul 2015, Peter Zijlstra wrote: > >> Now the 'problem' is finding these special regions fast, the easy >> solution is the same as the one proposed for userspace, one big section. >> That way the interrupt only has to check if the IP is inside this >> section which is minimal effort. >> >> The down side is that all percpu ops would then end up being full >> function calls. Which on some archs is indeed faster than disabling >> interrupts, but not by much I'm afraid. > > Well one could move the entire functions that are using these ops into the > special sections. That is certainly an area requiring much more thought.
Hmm. > >> > optimize the x86 variants if interrupts also can detect critical sections >> > and restart at defined points. >> >> I really don't see how we can beat %GS prefixes with any such scheme. > > We may be able to avoid RMV sequences which allows the processor to better > schedule operations. True, but cmpxchg is, surprisingly, pretty fast. Crazy thought: At the risk of proposing something ridiculous, what if we had per-cpu memory mappings? We could do this at the cost of up to 2kB of memcpy whenever we switch mms. Expensive but maybe not a showstopper. --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
