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Date: Mon, 7 Sep 2009 16:14:37 +0800
From: "lookeylam" <lookeylam@gmail.com>
To: "linux-kernel" <linux-kernel@vger.kernel.org>
Subject: About CPU's Load Balance and CFS functions
Message-ID: <200909071614346093582@gmail.com>
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Hello:
         I am  not sure this  is the right maillist to ask this question. I just have a try.
         I have a test on Dell 1950 with 8 cpus on board for testing the apache by ab command. And I find that in 
         linux 2.6.18. The processes forked by apache are not well distributed on these 8 cpus.
         linux 2.6.23 is a little better than 2.6.18, but still some cpus are running busy and some cpus remains idle.
         While in  2.6.30, these 8 cpus are well used and the percentage of each cpu is nearly the same. And when I 
         start the control group with cpuset type with sched_relax_domain_level( with value 3,4,5). The result of ab is 50ms better than test results without control group. 
        
         I attribute this situation to to load_balance but not CFS, because CFS is just a scheduler for orgnizing the process inside one cpu, while load_balance is the main character to control the process and load between different cpus.
         But when i give out this conclusion, I confuse about the differences of these three kernels of load_balance.
         
         My questions are the above conclusion  is right or not? How would these situation happen and why? I read the code of the kernel but I am still not sure.
        
        Thanks.