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?
Node 3, zone Normal
pages free 2055926
min 1441
low 1801
high 2161
scanned 0
spanned 2097152
present 2068480
vm stats threshold: 98
--
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>