On Fri, May 11, 2007 at 07:18:33PM +0200, Peter Zijlstra wrote: > On Fri, 2007-05-11 at 18:52 +0200, Eric Dumazet wrote: > > > > But I personally find this new rw_mutex not scalable at all if you have > > some > > writers around. > > > > percpu_counter_sum is just a L1 cache eater, and O(NR_CPUS) > > Yeah, that is true; there are two occurences, the one in > rw_mutex_read_unlock() is not strictly needed for correctness. > > Write locks are indeed quite expensive. But given the ratio of > reader:writer locks on mmap_sem (I'm not all that familiar with other > rwsem users) this trade-off seems workable.
I guess the problem with that logic is assuming the mmap_sem read side always needs to be scalable. Given the ratio of threaded:unthreaded apps, maybe the trade-off swings away from favour? - 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/
