Messages in this thread Patch in this message | | | From | Rik van Riel <> | Subject | [PATCH 12/14] sched,fair: track cfs_rq->max_h_load for more legitimate h_weight | Date | Mon, 22 Jul 2019 13:33:46 -0400 |
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The cfs_rq->h_load decays to zero quite rapidly, which can easily lead to tasks getting enqueued with an h_weight and h_load of zero, confusing the load balancer, the preemption code, and other parts of the kernel.
Add a slow moving cfs_rq->max_h_load, with a half life of just over a minute, to help tasks get enqueued with more legitimate h_weight values.
Suggested-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Rik van Riel <riel@surriel.com> --- kernel/sched/debug.c | 2 ++ kernel/sched/fair.c | 6 +++++- kernel/sched/pelt.c | 16 ++++++++++++++++ kernel/sched/pelt.h | 1 + kernel/sched/sched.h | 2 ++ 5 files changed, 26 insertions(+), 1 deletion(-)
diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 6e7c8ff210a8..88ed6d4429e6 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -553,6 +553,8 @@ void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq) atomic_long_read(&cfs_rq->tg->load_avg)); SEQ_printf(m, " .%-30s: %lu\n", "h_load", cfs_rq->h_load); + SEQ_printf(m, " .%-30s: %lu\n", "max_h_load", + cfs_rq->max_h_load); #endif #endif #ifdef CONFIG_CFS_BANDWIDTH diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 1d5145cb6096..224cd9b20887 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7636,6 +7636,8 @@ static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq) if (!se) { cfs_rq->h_load = cfs_rq_load_avg(cfs_rq); + slow_decay(&cfs_rq->max_h_load, &cfs_rq->last_max_h_decay); + cfs_rq->max_h_load = max(cfs_rq->max_h_load, cfs_rq->h_load); cfs_rq->last_h_load_update = now; } @@ -7645,6 +7647,8 @@ static void update_cfs_rq_h_load(struct cfs_rq *cfs_rq) cfs_rq_load_avg(cfs_rq) + 1); cfs_rq = group_cfs_rq(se); cfs_rq->h_load = load; + slow_decay(&cfs_rq->max_h_load, &cfs_rq->last_max_h_decay); + cfs_rq->max_h_load = max(load, cfs_rq->max_h_load); cfs_rq->last_h_load_update = now; } } @@ -7660,7 +7664,7 @@ static unsigned long task_se_h_weight(struct sched_entity *se) update_cfs_rq_h_load(cfs_rq); /* Reduce the load.weight by the h_load of the group the task is in. */ - return (cfs_rq->h_load * se->load.weight) >> SCHED_FIXEDPOINT_SHIFT; + return (cfs_rq->max_h_load * se->load.weight) >> SCHED_FIXEDPOINT_SHIFT; } static unsigned long task_se_h_load(struct sched_entity *se) diff --git a/kernel/sched/pelt.c b/kernel/sched/pelt.c index 2c901e0f9fbd..2173db8c6209 100644 --- a/kernel/sched/pelt.c +++ b/kernel/sched/pelt.c @@ -58,6 +58,22 @@ static u64 decay_load(u64 val, u64 n) return val; } +/* + * Like above, with a period of close to a minute for very slow decay. + * At 2 seconds per period, LOAD_AVG_PERIOD periods is just over a minute. + */ +void slow_decay(unsigned long *load, unsigned long *time) +{ + unsigned long periods = (jiffies - *time) / 2; + + if (!periods) + return; + + *time += periods * 2; + + *load = decay_load(*load, periods); +} + static u32 __accumulate_pelt_segments(u64 periods, u32 d1, u32 d3) { u32 c1, c2, c3 = d3; /* y^0 == 1 */ diff --git a/kernel/sched/pelt.h b/kernel/sched/pelt.h index 1152c4ebf314..f16042e2aa06 100644 --- a/kernel/sched/pelt.h +++ b/kernel/sched/pelt.h @@ -6,6 +6,7 @@ int __update_load_avg_se(u64 now, struct cfs_rq *cfs_rq, struct sched_entity *se int __update_load_avg_cfs_rq(u64 now, struct cfs_rq *cfs_rq); int update_rt_rq_load_avg(u64 now, struct rq *rq, int running); int update_dl_rq_load_avg(u64 now, struct rq *rq, int running); +void slow_decay(unsigned long *load, unsigned long *time); #ifdef CONFIG_HAVE_SCHED_AVG_IRQ int update_irq_load_avg(struct rq *rq, u64 running); diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index b05fd87cf8b5..b627ca594f97 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -540,6 +540,8 @@ struct cfs_rq { * this group. */ unsigned long h_load; + unsigned long max_h_load; + unsigned long last_max_h_decay; u64 last_h_load_update; struct sched_entity *h_load_next; #endif /* CONFIG_FAIR_GROUP_SCHED */ -- 2.20.1
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