UDP-U stream performance regression on 32-rc1 kernel

Alex Shi
2009-11-03T03:45:56Z

We found the UDP-U 1k/4k stream of netperf benchmark have some
performance regression from 10% to 20% on our Tulsa and some NHM
machines. Bisecting found it is due to the following commitment.

commit 840a0653100dbde599ae8ddf83fa214dfa5fd1aa
Author: Ingo Molnar <mingo@elte.hu>
Date: Fri Sep 4 11:32:54 2009 +0200

sched: Turn on SD_BALANCE_NEWIDLE

Start the re-tuning of the balancer by turning on newidle.

It improves hackbench performance and parallelism on a 4x4 box.
The "perf stat --repeat 10" measurements give us:

domain0 domain1
.......................................
-SD_BALANCE_NEWIDLE -SD_BALANCE_NEWIDLE:
2041.273208 task-clock-msecs # 9.354 CPUs ( +- 0.363% )

+SD_BALANCE_NEWIDLE -SD_BALANCE_NEWIDLE:
2086.326925 task-clock-msecs # 11.934 CPUs ( +- 0.301% )

+SD_BALANCE_NEWIDLE +SD_BALANCE_NEWIDLE:
2115.289791 task-clock-msecs # 12.158 CPUs ( +- 0.263% )

BRGs
Alex