On 2017年11月29日 20:17, Michal Hocko wrote: > 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? To be honest, there are another two ways I can think of listed below. but I don't think they are simpler than my current implementation. Maybe you have better idea. static u64 __percpu vm_stat_numa[num_possible_nodes() * NR_VM_NUMA_STAT_ITEMS]; But it's not correct. Or we can add an u64 percpu array with size of NR_VM_NUMA_STAT_ITEMS in struct pglist_data. My current implementation is quite straightforward by combining all of local counters together, only one percpu array with size of num_possible_nodes()*NR_VM_NUMA_STAT_ITEMS is enough for that. > [...] >> +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 -- 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>
