linux-kernel - UDP-U stream performance regression on 32-rc1 kernel

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Message-Id: <1257220036.3819.193.camel@alexs-hp.sh.intel.com>
Date:	Tue, 03 Nov 2009 11:47:16 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	linux-kernel@...r.kernel.org
Cc:	mingo@...e.hu, "Zhang, Yanmin" <yanmin.zhang@...el.com>
Subject: UDP-U stream performance regression on 32-rc1 kernel

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@...e.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 

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