Stupid Load Question

[pjman]

I have been running a 1.3 MHZ Single CPU Red Hat 7.3 for about 5 years now. The average load on the system with 5 high traffic sites was (0.5) on 1 CPU.

I'm moving to a new server a 3.0 GHZ Dual Core Dempsey. The server now shows 8 CPUs. I have been looking around the forums and have come to realize that 8 CPUs really = 4 CPUs.

But as far as my load average on my new server would I 0.5 Load on a single CPU be the same as 2.0 Load on 4 CPUs.

I'm just wondering because I usually investigate any long loads over a 2.0 now. Should I not worry until it reaches an 8.0 now?

Any input is much appreciated.

 

[jayh38]

Your old box was single cpu therefore a load of 1 would be one full cycle to complete all the processes in line.

So your .5 load is indeed half your cpu cycle. After you go beyond a load of 1, you will start into your wait time so a load of 1.5 would effectively take 1 1/2 cycles to get through the current tasks.

So with your new box, a load of 2 would indeed require half of your cpu time which is equal to .5 on your old box, that is correct.

A load of 4 would be your full cpu cycle capacity given the threads are evenly stressed, with 0 wait time. You have effectively 4 cpu's multithreaded. You may not notice a lag or wait time until you hit a load of 6 to 8 and still not be a concern.

I have many dual quad boxes with extreme traffic that run happy and cool with a loading of 16 and show no signs of lag or stress. Amazing performance.

 

[pjman]

1000 Thanks for taking the time.

Finally I understand it. One less thing I have to ponder during my migration to the new box.

Thanks Again.