On Fri, Oct 22, 2021 at 12:06:13PM +1100, NeilBrown wrote:
> On Tue, 19 Oct 2021, Mel Gorman wrote:
> ...
> > + switch(reason) {
> > + case VMSCAN_THROTTLE_NOPROGRESS:
> > + case VMSCAN_THROTTLE_WRITEBACK:
> > + timeout = HZ/10;
> > +
> > + if (atomic_inc_return(&pgdat->nr_writeback_throttled) == 1) {
> > + WRITE_ONCE(pgdat->nr_reclaim_start,
> > + node_page_state(pgdat, NR_THROTTLED_WRITTEN));
>
> You have introduced a behaviour change that wasn't flagged in the commit
> message.
> Previously nr_writeback_throttled was only incremented for
> VMSCAN_THROTTLE_WRITEBACK, now it is incremented for
> VMSCAN_THROTTLE_NOPROGRESS as well.
>
> Some justification would be good.
>
This is the result of rebase near the end of a day going sideways. There
is no justification, it's just wrong.
I'm rerunning the entire series, will update the leader and resend the
series.
--8<--
mm/vmscan: Centralise timeout values for reclaim_throttle -fix
Neil Brown spotted the fallthrough-logic for reclaim_throttle was wrong --
only VMSCAN_THROTTLE_WRITEBACK affects pgdat->nr_writeback_throttled. This
was the result of a rebase going sideways and only happens to sometimes
work by co-incidence.
This is a fix to the mmotm patch
mm-vmscan-centralise-timeout-values-for-reclaim_throttle.patch
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
---
mm/vmscan.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 1f5c467dc83c..64c38979b7df 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -1032,7 +1032,6 @@ void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason)
* of the inactive LRU.
*/
switch(reason) {
- case VMSCAN_THROTTLE_NOPROGRESS:
case VMSCAN_THROTTLE_WRITEBACK:
timeout = HZ/10;
@@ -1041,6 +1040,9 @@ void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason)
node_page_state(pgdat, NR_THROTTLED_WRITTEN));
}
+ break;
+ case VMSCAN_THROTTLE_NOPROGRESS:
+ timeout = HZ/10;
break;
case VMSCAN_THROTTLE_ISOLATED:
timeout = HZ/50;
@@ -1055,7 +1057,7 @@ void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason)
ret = schedule_timeout(timeout);
finish_wait(wqh, &wait);
- if (reason == VMSCAN_THROTTLE_ISOLATED)
+ if (reason == VMSCAN_THROTTLE_WRITEBACK)
atomic_dec(&pgdat->nr_writeback_throttled);
trace_mm_vmscan_throttled(pgdat->node_id, jiffies_to_usecs(timeout),
