On Tue, 5 Feb 2008, Nick Piggin wrote: > Anyway, not saying the operations are useless, but they should be > made available to core kernel and implemented per-arch. (if they are > found to be useful)
The problem is to establish the usefulness. These measures may bring 1-2% in a pretty unstable operation mode assuming that the system is doing repetitive work. The micro optimizations seem to be often drowned out by small other changes to the system. There is the danger that a gain is seen that is not due to the patch but due to other changes coming about because code is moved since patches change execution paths. Plus they may be only possible on a specific architecture. I know that our IA64 hardware has special measures ensuring certain behavior of atomic ops etc, I guess Intel has similar tricks up their sleeve. At 8p there are likely increasing problems with lock starvation where your ticketlock helps. That is why I thought we better defer the stuff until there is some more evidence that these are useful. I got particularly nervous about these changes after I saw small performance drops due to the __unlock patch on the dual quad. That should have been a consistent gain. -- 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/
