sched: Fix granularity of task_u/stime() (761b1d26) · Commits · 戴 / test

Originally task_s/utime() were designed to return clock_t but later changed to return cputime_t by following commit: commit Author: Christian Borntraeger <borntraeger@de.ibm.com> Date: Thu Aug 23 15:18:02 2007 +0200 It only changed the type of return value, but not the implementation. As the result the granularity of task_s/utime() is still that of clock_t, not that of cputime_t. So using task_s/utime() in __exit_signal() makes values accumulated to the signal struct to be rounded and coarse grained. This patch removes casts to clock_t in task_u/stime(), to keep granularity of cputime_t over the calculation. v2: Use div_u64() to avoid error "undefined reference to `__udivdi3`" on some 32bit systems. Signed-off-by:

Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com> Acked-by:

Peter Zijlstra <peterz@infradead.org> Cc: xiyou.wangcong@gmail.com Cc: Spencer Candland <spencer@bluehost.com> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Stanislaw Gruszka <sgruszka@redhat.com> LKML-Reference: <4AFB9029.9000208@jp.fujitsu.com> Signed-off-by:

Ingo Molnar <mingo@elte.hu>

kernel/sched.c

+13 −9

Original line number	Diff line number	Diff line
		@@ -5156,41 +5156,45 @@ cputime_t task_stime(struct task_struct *p)
		return p->stime;
		}
		#else

		#ifndef nsecs_to_cputime
		# define nsecs_to_cputime(__nsecs) \
		msecs_to_cputime(div_u64((__nsecs), NSEC_PER_MSEC))
		#endif

		cputime_t task_utime(struct task_struct *p)
		{
		clock_t utime = cputime_to_clock_t(p->utime),
		total = utime + cputime_to_clock_t(p->stime);
		cputime_t utime = p->utime, total = utime + p->stime;
		u64 temp;

		/*
		* Use CFS's precise accounting:
		*/
		temp = (u64)nsec_to_clock_t(p->se.sum_exec_runtime);
		temp = (u64)nsecs_to_cputime(p->se.sum_exec_runtime);

		if (total) {
		temp *= utime;
		do_div(temp, total);
		}
		utime = (clock_t)temp;
		utime = (cputime_t)temp;

		p->prev_utime = max(p->prev_utime, clock_t_to_cputime(utime));
		p->prev_utime = max(p->prev_utime, utime);
		return p->prev_utime;
		}

		cputime_t task_stime(struct task_struct *p)
		{
		clock_t stime;
		cputime_t stime;

		/*
		* Use CFS's precise accounting. (we subtract utime from
		* the total, to make sure the total observed by userspace
		* grows monotonically - apps rely on that):
		*/
		stime = nsec_to_clock_t(p->se.sum_exec_runtime) -
		cputime_to_clock_t(task_utime(p));
		stime = nsecs_to_cputime(p->se.sum_exec_runtime) - task_utime(p);

		if (stime >= 0)
		p->prev_stime = max(p->prev_stime, clock_t_to_cputime(stime));
		p->prev_stime = max(p->prev_stime, stime);

		return p->prev_stime;
		}

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