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Message-ID: <BN6PR15MB1553DFF82A45A4E532B6DC119AF20@BN6PR15MB1553.namprd15.prod.outlook.com>
Date: Fri, 9 Feb 2018 17:59:12 +0000
From: Jon Maloy <jon.maloy@...csson.com>
To: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
"peterz@...radead.org" <peterz@...radead.org>,
"mingo@...nel.org" <mingo@...nel.org>
CC: "David Miller (davem@...emloft.net)" <davem@...emloft.net>
Subject: Serious performance degradation in Linux 4.15
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%
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