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The _sum and _avg values are in general sync together with the PELT divider. They are however not always completely in perfect sync, resulting in situations where _sum gets to zero while _avg stays positive. Such situations are undesirable. This comes from the fact that PELT will increase period_contrib, also increasing the PELT divider, without updating _sum and _avg values to stay in perfect sync where (_sum == _avg * divider). However, such PELT change will never lower _sum, making it impossible to end up in a situation where _sum is zero and _avg is not. Therefore, we need to ensure that when subtracting load outside PELT, that when _sum is zero, _avg is also set to zero. This occurs when (_sum < _avg * divider), and the subtracted (_avg * divider) is bigger or equal to the current _sum, while the subtracted _avg is smaller than the current _avg. Reported-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Reported-by: Naresh Kamboju <naresh.kamboju@linaro.org> Signed-off-by: Odin Ugedal <odin@uged.al> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org> Tested-by: Sachin Sant <sachinp@linux.vnet.ibm.com> Link: https://lore.kernel.org/r/20210624111815.57937-1-odin@uged.al |
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| .. | ||
| autogroup.c | ||
| autogroup.h | ||
| clock.c | ||
| completion.c | ||
| core_sched.c | ||
| core.c | ||
| cpuacct.c | ||
| cpudeadline.c | ||
| cpudeadline.h | ||
| cpufreq_schedutil.c | ||
| cpufreq.c | ||
| cpupri.c | ||
| cpupri.h | ||
| cputime.c | ||
| deadline.c | ||
| debug.c | ||
| fair.c | ||
| features.h | ||
| idle.c | ||
| isolation.c | ||
| loadavg.c | ||
| Makefile | ||
| membarrier.c | ||
| pelt.c | ||
| pelt.h | ||
| psi.c | ||
| rt.c | ||
| sched-pelt.h | ||
| sched.h | ||
| smp.h | ||
| stats.c | ||
| stats.h | ||
| stop_task.c | ||
| swait.c | ||
| topology.c | ||
| wait_bit.c | ||
| wait.c | ||