On Tue 28-11-17 14:00:23, Kemi Wang wrote: > The existed implementation of NUMA counters is per logical CPU along with > zone->vm_numa_stat[] separated by zone, plus a global numa counter array > vm_numa_stat[]. However, unlike the other vmstat counters, numa stats don't > effect system's decision and are only read from /proc and /sys, it is a > slow path operation and likely tolerate higher overhead. Additionally, > usually nodes only have a single zone, except for node 0. And there isn't > really any use where you need these hits counts separated by zone. > > Therefore, we can migrate the implementation of numa stats from per-zone to > per-node, and get rid of these global numa counters. It's good enough to > keep everything in a per cpu ptr of type u64, and sum them up when need, as > suggested by Andi Kleen. That's helpful for code cleanup and enhancement > (e.g. save more than 130+ lines code). I agree. Having these stats per zone is a bit of overcomplication. The only consumer is /proc/zoneinfo and I would argue this doesn't justify the additional complexity. Who does really need to know per zone broken out numbers? Anyway, I haven't checked your implementation too deeply but why don't you simply define static percpu array for each numa node? [...] > +extern u64 __percpu *vm_numa_stat; [...] > +#ifdef CONFIG_NUMA > + size = sizeof(u64) * num_possible_nodes() * NR_VM_NUMA_STAT_ITEMS; > + align = __alignof__(u64[num_possible_nodes() * NR_VM_NUMA_STAT_ITEMS]); > + vm_numa_stat = (u64 __percpu *)__alloc_percpu(size, align); > +#endif -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
