Re: times()
Glynn Clements <[email protected]>
| Newsgroups | org.kernel.vger.linux-c-programming |
|---|---|
| Message-ID | <[email protected]> |
João Fernandes Simplício wrote: > I've been testing the times() function and I can't understand in what > way is the ticking being incremented for system time measurement > (tms_stime). I understand that tms_utime gives the ticking related to > the process and what does tms_stime gives? tms_utime is the amount of CPU time spent executing user-space code (i.e. the executable and shared libraries), while tms_stime is the amount of CPU time spent in the kernel. > E.g.: > > In 5 minutes the process gives 10000 ticks, so if the OS supports a > maximum of 32758 process identifiers this gives us a 30% of load. > > Is my thinking right or am I missing something else? The number of PIDs doesn't come into it. times() reports the CPU time used by a single process. If sysconf(_SC_CLK_TCK) is 100, then 5 minutes is 5*60*100 = 30000 ticks, so 10000 ticks corresponds to 33% of the CPU time being used by that process. Also, note that 100% correponds to full utilisation of a single CPU. If you have multiple CPUs (a single CPU chip with multiple cores is treated as multiple CPUs), a multi-threaded process can exceed 100% CPU. -- Glynn Clements <[email protected]> -- To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html