On Tue, 13 Oct 2009 04:03:45 +0900 (JST) KOSAKI Motohiro <[email protected]> wrote:
> > Start simple. What's wrong with mutex_lock() on the reader and writer > > sides? rwsems might be OK too. > > > > In both cases we should think about whether persistent readers can > > block the writer excessively though. > > I thought your mention seems reasonable. then I mesured various locking > performance. > > no-contention read-read contetion read-write contention > w/o patch 4627 ms 7575 ms N/A > mutex 5717 ms 33872 ms (!) 14793 ms > rw-semaphoe 6846 ms 10734 ms 36156 ms (!) > seqlock 4754 ms 7558 ms 9373 ms > > Umm, seqlock is significantly better than other. Sure, but even the worst case there is 1,000,000 operations in 34 seconds (yes?). 33 microseconds for a /proc read while under a specific local DoS attack is OK! If so then all implementations are acceptable and we should choose the simplest, most-obviously-correct one. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
