On Fri, 21 Mar 2014 20:48:22 +0700, Anh Le said: > I'm studying the CFS scheduler. I'm using ubuntu 13.10 and I assume that > it's using CFS in it kernel. > > I try to see the effect of nice value by running 2 instances of the same > program (just a while loop of calculations), putting them on the same CPU > and setting different nice values to them (one is 19 and one is -20). I > include in the program some printf to see how much it has executed. > > According to my understanding, the process with the small nice value should > get more processor time than the one with the big value. However they seem > to be on par with each other (they execute approximately the same number of > loops in the same duration), so I'm really confused.
If you have 2 cores and 2 CPU-bound processes, one process will park on each core and get close to 100% of the cycles. Try it with 2 instances per core/hyperthread available. Look in /proc/cpuinfo to find how many you need.
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