On 2017年12月21日 16:59, Michal Hocko wrote: > On Thu 21-12-17 16:23:23, kemi wrote: >> >> >> On 2017年12月21日 16:17, Michal Hocko wrote: > [...] >>> Can you see any difference with a more generic workload? >>> >> >> I didn't see obvious improvement for will-it-scale.page_fault1 >> Two reasons for that: >> 1) too long code path >> 2) server zone lock and lru lock contention (access to buddy system >> frequently) > > OK. So does the patch helps for anything other than a microbenchmark? > >>>> Some thinking about that: >>>> a) the overhead due to cache bouncing caused by NUMA counter update in >>>> fast path >>>> severely increase with more and more CPUs cores >>> >>> What is an effect on a smaller system with fewer CPUs? >>> >> >> Several CPU cycles can be saved using single thread for that. >> >>>> b) AFAIK, the typical usage scenario (similar at least)for which this >>>> optimization can >>>> benefit is 10/40G NIC used in high-speed data center network of cloud >>>> service providers. >>> >>> I would expect those would disable the numa accounting altogether. >>> >> >> Yes, but it is still worthy to do some optimization, isn't? > > Ohh, I am not opposing optimizations but you should make sure that they > are worth the additional code and special casing. As I've said I am not > convinced special casing numa counters is good. You can play with the > threshold scaling for larger CPU count but let's make sure that the > benefit is really measurable for normal workloads. Special ones will > disable the numa accounting anyway. >
I understood. Could you give me some suggestion for those normal workloads, Thanks. I will have a try and post the data ASAP.
