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Posts: 1,224 | Thanked: 1,763 times | Joined on Jul 2007
#1602
Originally Posted by Rushmore View Post
Something seems to not make sense with Conky. Anyone notice that regardless of the clock speed, the percent of cpu usage stays fairly "constant"?

Example playing a 160KB MP3 with built-in media player:

Clock fluctuates from 125mhz on up to 800mhz, but the cpu usage percent ranges from 50% to 53%. I would expect both values (clock and usage) to be relative and not such a wide margin of fluctuation with the clock and usage. If one is constant, the other should be. I could see if there is lag for one value to the next, but that should be an issue of displacement of values, rather than one staying always "constant" (the usage).

BTW, most of the time, cpu is at 125mhz, but does fluctuate for several seconds up from 500 to 800, but usage does not deviate from 50% to 53% range.

The reason is that the kernel does not do exact accounting of CPU time - it only samples once for every slice (probably 10ms on N900, I did not check this), and accounts all the slice to the process, even if it uses only a part of the slice and then yields.

The way to get more accurate is to run another process that simply counts at a lower priority, and see how slower it becomes when an mp3 player is running. In this method mp3 players usually are over-reported, and use a lot less CPU than what seems.
I won't be surprised if pulse-audio also uses a lot less than what is always reported.
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