Peter Zijlstra <peterz@xxxxxxxxxxxxx> writes: > On Mon, Nov 04, 2019 at 10:41:10AM +0800, Huang, Ying wrote: > >> >> +#define NUMA_SCAN_NR_HIST 16 >> >> + int numa_scan_idx; >> >> + unsigned long numa_scan_jiffies[NUMA_SCAN_NR_HIST]; >> >> + unsigned long numa_scan_starts[NUMA_SCAN_NR_HIST]; >> > >> > Why 16? This is 4 cachelines. >> >> We want to keep the NUMA scanning history reasonably long. From >> task_scan_min(), the minimal interval between task_numa_work() running >> is about 100 ms by default. So we can keep 1600 ms history by default >> if NUMA_SCAN_NR_HIST is 16. If user choose to use smaller >> sysctl_numa_balancing_scan_size, then we can only keep shorter history. >> In general, we want to keep no less than 1000 ms history. So 16 appears >> like a reasonable choice for us. Any other suggestion? > > This is very good information for Changelogs and comments :-) Thanks! Will do this in the next version. Best Regards, Huang, Ying
