On Sat, Oct 16, 2010 at 07:26:48PM +0200, Peter Zijlstra wrote: > On Sat, 2010-10-16 at 12:27 +0200, Eric Dumazet wrote: > > > > In cases you mention, you want a precise count (aka > > percpu_counter_sum_positive()), not the approximate one (aka > > percpu_counter_read_positive()). > > > > The only difference is then the possible/online cpu loop difference. > > > In either case, SGI is screwed, doing millions of for_each_*_cpu() loops > per second isn't going to work for them. > > fwiw, for_each_*_cpu() takes longer than a single jiffy tick on those > machines. Yes, agreed. I'm not sure we need exact summation for these counters, but I haven't wanted to bring inaccuracies into the code at this point in time. I need to investigate the effect of using the approximate summation values in all the cases they are used. I don't see that there will be a problem doing this, but it's not something that needs to be cared about right now. After we get to the store-free path walks in place, we can revisit all these side issues more fully. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
