| Message ID | 20211019090108.25501-8-mgorman@techsingularity.net (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Remove dependency on congestion_wait in mm/ | expand |
On Tue, 19 Oct 2021, Mel Gorman wrote: > Tracing of the stutterp workload showed the following delays > > 1 usect_delayed=124000 reason=VMSCAN_THROTTLE_NOPROGRESS > 1 usect_delayed=128000 reason=VMSCAN_THROTTLE_NOPROGRESS > 1 usect_delayed=176000 reason=VMSCAN_THROTTLE_NOPROGRESS > 1 usect_delayed=536000 reason=VMSCAN_THROTTLE_NOPROGRESS > 1 usect_delayed=544000 reason=VMSCAN_THROTTLE_NOPROGRESS > 1 usect_delayed=556000 reason=VMSCAN_THROTTLE_NOPROGRESS > 1 usect_delayed=624000 reason=VMSCAN_THROTTLE_NOPROGRESS > 1 usect_delayed=716000 reason=VMSCAN_THROTTLE_NOPROGRESS > 1 usect_delayed=772000 reason=VMSCAN_THROTTLE_NOPROGRESS > 2 usect_delayed=512000 reason=VMSCAN_THROTTLE_NOPROGRESS > 16 usect_delayed=120000 reason=VMSCAN_THROTTLE_NOPROGRESS > 53 usect_delayed=116000 reason=VMSCAN_THROTTLE_NOPROGRESS > 116 usect_delayed=112000 reason=VMSCAN_THROTTLE_NOPROGRESS > 5907 usect_delayed=108000 reason=VMSCAN_THROTTLE_NOPROGRESS > 71741 usect_delayed=104000 reason=VMSCAN_THROTTLE_NOPROGRESS > > All the throttling hit the full timeout and then there was wakeup delays > meaning that the wakeups are premature as no other reclaimer such as > kswapd has made progress. This patch increases the maximum timeout. Would love to see the comparable tracing results for after the patch. Thanks, NeilBrown > > Signed-off-by: Mel Gorman <mgorman@techsingularity.net> > Acked-by: Vlastimil Babka <vbabka@suse.cz> > --- > mm/vmscan.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 1f5c467dc83c..ec2006680242 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -1033,6 +1033,8 @@ void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason) > */ > switch(reason) { > case VMSCAN_THROTTLE_NOPROGRESS: > + timeout = HZ/2; > + break; > case VMSCAN_THROTTLE_WRITEBACK: > timeout = HZ/10; > > -- > 2.31.1 > >
On Fri, Oct 22, 2021 at 12:07:43PM +1100, NeilBrown wrote: > On Tue, 19 Oct 2021, Mel Gorman wrote: > > Tracing of the stutterp workload showed the following delays > > > > 1 usect_delayed=124000 reason=VMSCAN_THROTTLE_NOPROGRESS > > 1 usect_delayed=128000 reason=VMSCAN_THROTTLE_NOPROGRESS > > 1 usect_delayed=176000 reason=VMSCAN_THROTTLE_NOPROGRESS > > 1 usect_delayed=536000 reason=VMSCAN_THROTTLE_NOPROGRESS > > 1 usect_delayed=544000 reason=VMSCAN_THROTTLE_NOPROGRESS > > 1 usect_delayed=556000 reason=VMSCAN_THROTTLE_NOPROGRESS > > 1 usect_delayed=624000 reason=VMSCAN_THROTTLE_NOPROGRESS > > 1 usect_delayed=716000 reason=VMSCAN_THROTTLE_NOPROGRESS > > 1 usect_delayed=772000 reason=VMSCAN_THROTTLE_NOPROGRESS > > 2 usect_delayed=512000 reason=VMSCAN_THROTTLE_NOPROGRESS > > 16 usect_delayed=120000 reason=VMSCAN_THROTTLE_NOPROGRESS > > 53 usect_delayed=116000 reason=VMSCAN_THROTTLE_NOPROGRESS > > 116 usect_delayed=112000 reason=VMSCAN_THROTTLE_NOPROGRESS > > 5907 usect_delayed=108000 reason=VMSCAN_THROTTLE_NOPROGRESS > > 71741 usect_delayed=104000 reason=VMSCAN_THROTTLE_NOPROGRESS > > > > All the throttling hit the full timeout and then there was wakeup delays > > meaning that the wakeups are premature as no other reclaimer such as > > kswapd has made progress. This patch increases the maximum timeout. > > Would love to see the comparable tracing results for after the patch. > They're in the leader. The trace figures in the changelog are the ones I had at the time the patch was developed and I didn't keep them up to date to reduce overall test time. At the last set of results, some throttling was still hitting the full timeout; [....] 843 usec_timeout=500000 usect_delayed=12000 reason=VMSCAN_THROTTLE_NOPROGRESS 1299 usec_timeout=500000 usect_delayed=104000 reason=VMSCAN_THROTTLE_NOPROGRESS 2839 usec_timeout=500000 usect_delayed=8000 reason=VMSCAN_THROTTLE_NOPROGRESS 10111 usec_timeout=500000 usect_delayed=4000 reason=VMSCAN_THROTTLE_NOPROGRESS 21492 usec_timeout=500000 usect_delayed=0 reason=VMSCAN_THROTTLE_NOPROGRESS 36441 usec_timeout=500000 usect_delayed=500000 reason=VMSCAN_THROTTLE_NOPROGRESS
diff --git a/mm/vmscan.c b/mm/vmscan.c index 1f5c467dc83c..ec2006680242 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -1033,6 +1033,8 @@ void reclaim_throttle(pg_data_t *pgdat, enum vmscan_throttle_state reason) */ switch(reason) { case VMSCAN_THROTTLE_NOPROGRESS: + timeout = HZ/2; + break; case VMSCAN_THROTTLE_WRITEBACK: timeout = HZ/10;
Tracing of the stutterp workload showed the following delays 1 usect_delayed=124000 reason=VMSCAN_THROTTLE_NOPROGRESS 1 usect_delayed=128000 reason=VMSCAN_THROTTLE_NOPROGRESS 1 usect_delayed=176000 reason=VMSCAN_THROTTLE_NOPROGRESS 1 usect_delayed=536000 reason=VMSCAN_THROTTLE_NOPROGRESS 1 usect_delayed=544000 reason=VMSCAN_THROTTLE_NOPROGRESS 1 usect_delayed=556000 reason=VMSCAN_THROTTLE_NOPROGRESS 1 usect_delayed=624000 reason=VMSCAN_THROTTLE_NOPROGRESS 1 usect_delayed=716000 reason=VMSCAN_THROTTLE_NOPROGRESS 1 usect_delayed=772000 reason=VMSCAN_THROTTLE_NOPROGRESS 2 usect_delayed=512000 reason=VMSCAN_THROTTLE_NOPROGRESS 16 usect_delayed=120000 reason=VMSCAN_THROTTLE_NOPROGRESS 53 usect_delayed=116000 reason=VMSCAN_THROTTLE_NOPROGRESS 116 usect_delayed=112000 reason=VMSCAN_THROTTLE_NOPROGRESS 5907 usect_delayed=108000 reason=VMSCAN_THROTTLE_NOPROGRESS 71741 usect_delayed=104000 reason=VMSCAN_THROTTLE_NOPROGRESS All the throttling hit the full timeout and then there was wakeup delays meaning that the wakeups are premature as no other reclaimer such as kswapd has made progress. This patch increases the maximum timeout. Signed-off-by: Mel Gorman <mgorman@techsingularity.net> Acked-by: Vlastimil Babka <vbabka@suse.cz> --- mm/vmscan.c | 2 ++ 1 file changed, 2 insertions(+)