On Monday 19 October 2015 11:20 AM, Andi Kleen wrote: > Vineet Gupta <[email protected]> writes: >> But this user space - so IMHO UP/SMP doesn't matter and we can't simulate >> them in >> C just by itself. > It matters when you access the perf ring buffer which is updated by kernel.
That's part of the problem. The issue is with atomic_* APIs proliferation in perf user space code which assumes native atomix r-m-w support which is not always true. So I think we still need a feature detection mechanism and if absent leave the ball in arch court by calling arch_atomic_* which can use creative or half working measures so perf will work to some extent atleast and not bomb outright. Also can u please elaborate a bit on "simulate them in C" - u mean just simple unprotected LD, OP, ST or do u fancy usage of futex etc? > Also perf is now multi threaded to some degree. -- To unsubscribe from this list: send the line "unsubscribe linux-perf-users" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
