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Date: Tue, 03 Nov 2009 12:33:10 +0800 From: "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com> To: alex.shi@...el.com Cc: linux-kernel@...r.kernel.org, mingo@...e.hu, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Mike Galbraith <efault@....de> Subject: Re: UDP-U stream performance regression on 32-rc1 kernel On Tue, 2009-11-03 at 11:47 +0800, Alex Shi wrote: > 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. perf events shows function find_busiest_group consumes about 4.5% cpu time with the patch while it only consumes 0.5% cpu time without the patch. The communication between netperf client and netserver is very fast. When netserver receives a message and there is no new message available, it goes to sleep and scheduler calls idle_balance => load_balance_newidle. load_balance_newidle spends too much time and a new message arrives quickly before load_balance_newidle ends. As the comments in the patch say hackbench benefits from it, I tested hackbench on Nehalem and core2 machines. hackbench does benefit from it, about 6% on nehalem machines, but doesn't benefit on core2 machines. Yanmin > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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