On Fri 15-09-17 07:16:23, Dave Hansen wrote: > On 09/15/2017 04:49 AM, Michal Hocko wrote: > > Why do we need an auto-mode? Is it safe to enforce by default. > > Do we *need* it? Not really. > > But, it does offer the best of both worlds: The vast majority of users > see virtually no impact from the counters. The minority that do need > them pay the cost *and* don't have to change their tooling at all. Just to make it clear, I am not really opposing. It just adds some code which we can safe... It is also rather chatty for something that can be true/false. > > Is it> possible that userspace can get confused to see 0 NUMA stats in > the > > first read while other allocation stats are non-zero? > > I doubt it. Those counters are pretty worthless by themselves. I have > tooling that goes and reads them, but it aways displays deltas. Read > stats, sleep one second, read again, print the difference. This is how I use them as well. > The only scenario I can see mattering is someone who is seeing a > performance issue due to NUMA allocation misses (or whatever) and wants > to go look *back* in the past. yes > A single-time printk could also go a long way to keeping folks from > getting confused. -- Michal Hocko SUSE Labs
