[PATCH 0/1] sched: defer idle accounting till after load update period

[Chase Douglas]

The following patch fixes a load avg calculation bug. Details are included with
the patch. Essentially, a task that often runs for less than 10 ticks at a time
is likely to be left out of the load avg calculation. A test case is provided
below. If you run the test case on a near zero-load system you will find top
report 90% cpu usage while the load avg stays at or near 0.00. With the patch,
the load avg is calculated correctly to be at least 0.90.

--

#include <asm/param.h>
#include <sys/time.h>
#include <time.h>

int main() {
	struct timespec ts;
	ts.tv_sec = 0;
	ts.tv_nsec = 1000000000 / HZ;

	/*
	 * Run gettimeofday in a tight loop 9 ticks, then sleep for 1 tick
	 */
	while (1) {
		struct timeval tv;

		do {
			gettimeofday(&tv, NULL);
		} while ((tv.tv_usec * HZ / 1000000) % 10 != 0);

		nanosleep(&ts, NULL);
	}
	return 0;
}
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