The two commits
d153b153446f7 (" sched/core: Fix wake_affine() performance regression") and
f2cdd9cc6c97 ("sched/core: Address more wake_affine() regressions")
are causing a serious performance degradation in Linux 4.5.
The effect is worst on TIPC, but even TCP is affected, as the figures below
show.
Command for TCP:
"netperf TCP_STREAM (netperf -n 4 -f m -c 4 -C 4 -P 1 -H 10.0.0.1 -t TCP_STREAM
-l 10 -- -O THROUGHPUT)"
v4.15-rc1 without f2cdd9cc6c97e, d153b153446f7: 1293.67
V4.15 with the two commits: 1104.58
i.e., a degradation of 17 % for TCP
Command for TIPC:
"netperf TIPC_STREAM (netperf -n 4 -f m -c 4 -C 4 -P 1 -H 10.0.0.1 -t
TCP_STREAM -l 10 -- -O THROUGHPUT)"
v4.15-rc1 without f2cdd9cc6c97e, d153b153446f7: 786.22
V4.15 with the two commits: 223.18
i.e., a degradation of 71 %
This is really bad, and I hope you have a plan for reintroducing this in some
form.
BR
Jon Maloy
v4.15-rc1->latest diff (%)
"netperf TCP_STREAM (netperf -n 4 -f m -c 4 -C 4 -P 1 -H 10.0.0.1 -t TCP_STREAM
-l 10 -- -O THROUGHPUT)" 1293.67 1104.58 -14.62%
"benchmark TIPC
(client_bench -c 1 -m 65000 -t)" 786.67 215.67 -72.58%
"netperf TIPC_STREAM
(netperf -n 4 -f m -c 4 -C 4 -P 1 -H 10.0.0.1 -t TIPC_STREAM -l 10 -- -O
THROUGHPUT)" 786.22 223.18 -71.61%
