Hi Naoya, On Tue, Dec 10, 2013 at 01:44:35AM -0500, Naoya Horiguchi wrote: >Hi Wanpeng, > >On Sun, Dec 08, 2013 at 02:14:50PM +0800, Wanpeng Li wrote: >> commit 04bb2f947 (sched/numa: Adjust scan rate in task_numa_placement) calculate >> period_slot which should be used as base value of scan rate increase if remote >> access dominate. However, current codes forget to use it, this patch fix it. >> >> Signed-off-by: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx> >> --- >> kernel/sched/fair.c | 2 +- >> 1 files changed, 1 insertions(+), 1 deletions(-) >> >> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c >> index 7073c76..b077f1b3 100644 >> --- a/kernel/sched/fair.c >> +++ b/kernel/sched/fair.c >> @@ -1358,7 +1358,7 @@ static void update_task_scan_period(struct task_struct *p, >> */ >> period_slot = DIV_ROUND_UP(diff, NUMA_PERIOD_SLOTS); >> ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared)); >> - diff = (diff * ratio) / NUMA_PERIOD_SLOTS; >> + diff = (period_slot * ratio) / NUMA_PERIOD_SLOTS; >> } >> >> p->numa_scan_period = clamp(p->numa_scan_period + diff, > >It seems to me that the original code is correct, because the mathematical >meaning of this hunk is clear: > > diff = (diff calculated by local-remote ratio) * (private-shared ratio) > >If you use period_slot here, diff always becomes less then 1/10 finally by >the second ratio multiplication (because we divide by NUMA_PERIOD_SLOTS twice), >and I don't see the justification. > >And if my idea is correct, we don't have to recalculate period_slot when >we multiply private-shared ratio. So we can remove that line. Thanks for your review. I agree with you when I first review this codes. It introduced by commit 04bb2f94 (sched/numa: Adjust scan rate in task_numa_placement), what's your original target, Rik ? > >Thanks, >Naoya Horiguchi -- 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>