![]() The get resource usage (getrusage) system call gives the process execution time in the struct timeval, with time in seconds and microseconds. Overall, the elapsed time between the first and the second calls is 40 ms. The above program gives the following output on my machine,Īs per the above output, the system has spent 30 ms in executing instructions between the first and the second call to call to times system call. Tms1.tms_cutime, tms1.tms_stime, tms1.tms_cstime) Printf ("ct1 = %ld, times: %ld %ld %ld %ld\n", ct1, tms1.tms_utime, Tms0.tms_cutime, tms0.tms_stime, tms0.tms_cstime) Printf ("ct0 = %ld, times: %ld %ld %ld %ld\n", ct0, tms0.tms_utime, An example program using the times and sysconf (_SC_CLK_TCK) system calls is, To convert the clock_t values, returned by times, into seconds one has to divide by the number of clock ticks per second. That is, in this case, there is a clock tick every 10 milliseconds or 0.01 second. Printf ("_SC_CLK_TCK = %ld\n", sysconf (_SC_CLK_TCK)) Ī typical value of clock ticks per second is 100. The number of clock ticks per second can be found by the sysconf system call, However, the data returned in the buffer is of interest to us as it gives us the user and system time for the process and its children which have terminated and for which the parent has issued a wait system call. times returns time since some arbitrary point back in time. The user and system times are passed back in the buffer. */Ĭlock_t tms_cstime /* System CPU time of terminated children. */Ĭlock_t tms_cutime /* User CPU time of terminated children. There is a struct tms,Ĭlock_t tms_stime /* System CPU time. The times system call gives the time spent by the CPU on a given process. +#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE Kernel/sched/cputime.c | 34 +++++++++-Ĥ files changed, 38 insertions(+), 36 deletions(-)ĭiff -git a/include/linux/init_task.h b/include/linux/init_task.h Our utime will be larger than it should be, making the above problem If the computed stime is smaller then the previously returned stime, There is also an issue with calculating utime as rtime - stime, where is One advances stime while the other advances utime such that the sum will This means that when the s/u-time sample values are small, and changeĬan shift the balance quickly, concurrent updaters can race such that Subject: sched,cputime: Serialize cputime_adjust()įredrik reports that top and other tools can occasionally observe >100%Ĭpu usage and reports that this is because cputime_adjust() callers are ![]() Therefore, find attached a version that has a per task/signal lock. Now, while you're probably right in that contention is unlikely for saneīehaviour, I could imagine some perverted apps hammering Platforms, the thing needs a lock indeed. Indeed, and barring cmpxchg_double(), which is not available on all > Hello Peter, your patch helps with some of the cases but not all: Sorry for the delay, I seem to have gotten distracted. Next in thread: Fredrik MarkstrÃm: "Re: cputime: Make the reported utime+stime correspond to the actual runtime.".Previous message: Tomeu Vizoso: " gpiolib: Fix docs for gpiochip_add_pingroup_range".Next message: Christoph Lameter: "Re: mm: fix status code move_pages() returns for zero page".Re: cputime: Make the reported utime+stime correspond to the actual runtime. Linux-Kernel Archive: Re: cputime: Make the reported utime+stime correspond to the actual runtime.
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