From 63f202e5edf161c2ccffa286a9a701e995427b15 Mon Sep 17 00:00:00 2001 From: "Rafael J. Wysocki" Date: Wed, 13 Nov 2019 01:03:24 +0100 Subject: [PATCH] cpuidle: teo: Avoid using "early hits" incorrectly If the current state with the maximum "early hits" metric in teo_select() is also the one "matching" the expected idle duration, it will be used as the candidate one for selection even if its "misses" metric is greater than its "hits" metric, which is not correct. In that case, the candidate state should be shallower than the current one and its "early hits" metric should be the maximum among the idle states shallower than the current one. To make that happen, modify teo_select() to save the index of the state whose "early hits" metric is the maximum for the range of states below the current one and go back to that state if it turns out that the current one should be rejected. Fixes: 159e48560f51 ("cpuidle: teo: Fix "early hits" handling for disabled idle states") Signed-off-by: Rafael J. Wysocki --- drivers/cpuidle/governors/teo.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-) diff --git a/drivers/cpuidle/governors/teo.c b/drivers/cpuidle/governors/teo.c index b33418f5df70..f5dfeed77f0a 100644 --- a/drivers/cpuidle/governors/teo.c +++ b/drivers/cpuidle/governors/teo.c @@ -239,7 +239,7 @@ static int teo_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, s64 latency_req = cpuidle_governor_latency_req(dev->cpu); u64 duration_ns; unsigned int hits, misses, early_hits; - int max_early_idx, constraint_idx, idx, i; + int max_early_idx, prev_max_early_idx, constraint_idx, idx, i; ktime_t delta_tick; if (dev->last_state_idx >= 0) { @@ -256,6 +256,7 @@ static int teo_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, misses = 0; early_hits = 0; max_early_idx = -1; + prev_max_early_idx = -1; constraint_idx = drv->state_count; idx = -1; @@ -307,6 +308,7 @@ static int teo_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, */ if (!(tick_nohz_tick_stopped() && drv->states[idx].target_residency_ns < TICK_NSEC)) { + prev_max_early_idx = max_early_idx; early_hits = cpu_data->states[i].early_hits; max_early_idx = idx; } @@ -333,6 +335,7 @@ static int teo_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, if (early_hits < cpu_data->states[i].early_hits && !(tick_nohz_tick_stopped() && drv->states[i].target_residency_ns < TICK_NSEC)) { + prev_max_early_idx = max_early_idx; early_hits = cpu_data->states[i].early_hits; max_early_idx = i; } @@ -346,9 +349,19 @@ static int teo_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, * "early hits" metric, but if that cannot be determined, just use the * state selected so far. */ - if (hits <= misses && max_early_idx >= 0) { - idx = max_early_idx; - duration_ns = drv->states[idx].target_residency_ns; + if (hits <= misses) { + /* + * The current candidate state is not suitable, so take the one + * whose "early hits" metric is the maximum for the range of + * shallower states. + */ + if (idx == max_early_idx) + max_early_idx = prev_max_early_idx; + + if (max_early_idx >= 0) { + idx = max_early_idx; + duration_ns = drv->states[idx].target_residency_ns; + } } /* -- 2.30.2