On Fri, 2011-04-29 at 22:43 +0800, Tejun Heo wrote: > Hello, > > On Fri, Apr 29, 2011 at 09:25:09AM -0500, Christoph Lameter wrote: > > On Fri, 29 Apr 2011, Tejun Heo wrote: > > > > > > If someone wants more accuracy then we need the ability to dynamically set > > > > the batch limit similar to what the vm statistics do. > > > > > > So, if you can remove _sum() by doing the above without introducing > > > excessive complexity or penalizing use cases which might not have too > > > much commonality with vmstat, by all means, but please pay attention > > > to the current users. Actually take a look at them. > > > > I am content to be maintaining the vm statistics.... But Shaohua may want > > to have a look at it? > > It would be nice if vmstat can be merged with percpu counter tho so > that the flushing can be done together. If we such piggybacking, the > flushing overhead becomes much easier to justify. > > How does vmstat collect the percpu counters? Does one cpu visit all > of them or each cpu flush local counter to global one periodically? I thought we can use a lglock like locking to address the issue. each cpu holds its lock to do update. _sum hold all cpu's lock to get consistent result. This will slow down _sum a little bit, but assume this doesn't matter. I haven't checked if we can still make fast path preemptless, but we use atomic now. This can still give me similar performance boost like previous implementation. Thanks, Shaohua -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>