On Tue, 28 Sep 2010, Shaohua Li wrote: > In a 4 socket 64 CPU system, zone_nr_free_pages() takes about 5% ~ 10% cpu time > according to perf when memory pressure is high. The workload does something > like: > for i in `seq 1 $nr_cpu` > do > create_sparse_file $SPARSE_FILE-$i $((10 * mem / nr_cpu)) > $USEMEM -f $SPARSE_FILE-$i -j 4096 --readonly $((10 * mem / nr_cpu)) & > done > this simply reads a sparse file for each CPU. Apparently the > zone->percpu_drift_mark is too big, and guess zone_page_state_snapshot() makes > a lot of cache bounce for ->vm_stat_diff[]. below is the zoneinfo for reference. > Is there any way to reduce the overhead? I guess Mel could reduce the percpu_drift_mark? Or tune that with a reduction in the stat_threshold? The less the count can deviate the less the percpu_drift_mark has to be and the less we need calls to zone_page_state_snapshot. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>