Messages in this thread | | | From | "" <> | Subject | Utime and stime are less when getrusage (RUSAGE_THREAD) is executed on a tickless CPU. | Date | Wed, 12 May 2021 03:28:02 +0000 |
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Hello.
I found that when I run getrusage(RUSAGE_THREAD) on a tickless CPU, the utime and stime I get are less than the actual time, unlike when I run getrusage(RUSAGE_SELF) on a single thread. This problem seems to be caused by the fact that se.sum_exec_runtime is not updated just before getting the information from 'current'. In the current implementation, task_cputime_adjusted() calls task_cputime() to get the 'current' utime and stime, then calls cputime_adjust() to adjust the sum of utime and stime to be equal to cputime.sum_exec_runtime. On a tickless CPU, sum_exec_runtime is not updated periodically, so there seems to be a discrepancy with the actual time. Therefore, I think I should include a process to update se.sum_exec_runtime just before getting the information from 'current' (as in other processes except RUSAGE_THREAD). I'm thinking of the following improvement.
@@ void getrusage(struct task_struct *p, int who, struct rusage *r) if (who == RUSAGE_THREAD) { + task_sched_runtime(current); task_cputime_adjusted(current, &utime, &stime);
Is there any possible problem with this?
Thanks. Hitomi Hasegawa
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