Top gives me an output like:
%Cpu(s): 4.7 us, 1.3 sy, 0.0 ni, 93.9 id, 0.1 wa, 0.0 hi, 0.0 si, 0.0 st
if my CPU has spent 4.7% of its time on user processes, how much of time history has it considered before coming up with such a result?
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Search for "how does linux top work" gives the following as the top (pun intended) result where does top gets real-time data– DavidPostill ♦Commented Oct 27, 2014 at 20:19
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@DavidPostill, right. So is it based on idle and non-idle times read ever since the CPU started? The link doesn't mention that, forgive me.– learnerCommented Oct 27, 2014 at 20:23
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1 Answer
From where does top gets real-time data, answer by bdonlan:
As documented in proc(5), in the file
/proc/(pid)/statyou have the fields:
utime %luAmount of time that this process has been scheduled in user mode, measured in clock ticks (divide by sysconf(_SC_CLK_TCK). This includes guest time, guest_time (time spent running a virtual CPU, see below), so that applications that are not aware of the guest time field do not lose that time from their calculations.
stime %luAmount of time that this process has been scheduled in kernel mode, measured in clock ticks (divide by sysconf(_SC_CLK_TCK).
answered Oct 27, 2014 at 20:24
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does this mean that these values are measured since when the process/CPU started?– learnerCommented Oct 27, 2014 at 20:32