Hi all, since I have played a bit with the kernel sources these are some newbie questions, that I couldn't find with trivial search engine usage; a) It is possible to use gcc builtin functions in conjuction with some gcc switches and the march to produce somewhat optimal code. For instance function __builtin_popcount, together with the march=amdfam10 and -mabm produces a POPCNT assembly instruction which counts the bits on word (machine word) in 1 instruction. For archs that does not support the popcnt instruction as far as I can tell gcc produces /normal-expected/ code that does the same thing in a simple (using a loop, shifting and counting Zero-Flags) or a more advanced way (). Is such programming practice condemned? b) One of the coolest things in kernel is the different types of I/O schedulers. I haven't exhaustively checked the source but is it possible to have a differnet I/O scheduler per device? If for instance I have an SSD and a normal hdd wouldn't be cooler to use noop I/O Sched for the SSD and anticipatory I/O Sched for the normal hdd? c) Is there a way to profile *just* one specific module/function/group of functions that run as a kernel thread for runtime performance? So far I've (tried to) used (use) oprofile (http://oprofile.sf.net) for some profiling and it is quite disturbing ( can't see the tree for the forest :P ). Cheers :) -- To unsubscribe from this list: send the line "unsubscribe linux-newbie" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.linux-learn.org/faqs
