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I'm using Debian 8 Linux distribution on 2 different PC configurations. The first configuration you will notice below is the one that I am using for a very long time. This configuration is using 100% cpu at high-peak times, so I decided to buy a new PC with much higher specs. I'm running an old 32bit linux app that has been launched more than 10 years ago, called samp03svr. This is a single-thread app, so I searched only for high frequency CPU. Xeon processors wouldn't help me. The app needs higher CPU frequency than number of cores.

Here are my PC configurations:

  1. An older configuration MotherBoard: ASUS P8H61-M Processor: Intel i5-3570 @ 3.4 GHz RAM: 2x8GB Kingston 1333MHz

  2. A newer configuration MotherBoard: B250M-D3H-CF Processor: i7-7700K CPU @ 4.20GHz RAM: 2x8GB Kingston 2133MHz

What I would expect from the newer configuration is a much lower CPU usage, but, surprise, this is not happening. In fact, the CPU usage is about 5 times higher than the older configuration. The tests I made were done for the same amount of workload, with the same operating system and the same drivers. I tried even to disable multi-thread but there is no CPU usage difference.

What would you recommend to do?

  • Have you tried a newer version of the program? Sounds like the old one may be buggy. – Herb Wolfe Mar 16 '17 at 10:37
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    You actually don't need a higher frequency you need a higher amount of instructions per cycle. If you're running the old machine at 100% how can the usage with a newer system be five times higher? – Seth Mar 16 '17 at 10:53
  • Herb Wolfe, there is no newer version of the program. Thanks for your interest. Seth, I can see from single core benchmarks that the i7 has a better score than the i5. I don't understand it's behavior. – Stefan Nechifor Mar 16 '17 at 11:39
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If your goal is to meet the demand during the peak times you mention, I would consider, if possible, running the server program on both machines you now have and putting them behind a load balancer, like haproxy.

On the other hand, if your goal is to reduce the CPU consumption of your server program, you have a couple of options.

You can lower the priority of your process so that the kernel will schedule its CPU time in such a way that it does not dominate your CPU. This can be done using the nice or renice commands. On Debian, the priority values range from -20 to +19, and the default value (launching a process without using nice) is 0. The higher the value, the lower the priority will be. It becomes easy to remember if you think of it like "the nicer a process, the more it is willing to give up its CPU time to other processes".

Launch your program like this using different niceness values:

nice -n +12 /path/to/your/program

If your program is already running, you can use renice with its pid:

#first find the pid
pgrep your_program_name
#or
ps aux | grep your_program_name

#now use the pid here
renice -n +12 pid_of_your_program

#or if you are comfortable combining these
renice -n +12 $(pgrep your_program_name)

Another option is using a tool called cpulimit. It lets you run a program and define the maximum percentage of the CPU you want to allow it.

#install the package
apt-get install cpulimit

#run your program, for example limiting to 25%
cpulimit -l 25 /path/to/your/program

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