Messages in this thread Patch in this message | | | From | "Rafael J. Wysocki" <> | Subject | [PATCH v2 2/3] cpuidle: teo: Avoid stopping the tick unnecessarily when bailing out | Date | Fri, 28 Jul 2023 12:00:46 +0200 |
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From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
When teo_select() is going to return early in some special cases, make it avoid stopping the tick if the idle state to be returned is shallow.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> --- drivers/cpuidle/governors/teo.c | 50 +++++++++++++++++++++++++--------------- 1 file changed, 32 insertions(+), 18 deletions(-)
Index: linux-pm/drivers/cpuidle/governors/teo.c =================================================================== --- linux-pm.orig/drivers/cpuidle/governors/teo.c +++ linux-pm/drivers/cpuidle/governors/teo.c @@ -462,9 +462,9 @@ static int teo_select(struct cpuidle_dri /* Avoid unnecessary overhead. */ if (idx < 0) { idx = 0; /* No states enabled, must use 0. */ - goto end; + goto bail_out; } else if (idx == idx0) { - goto end; + goto bail_out; } /* @@ -547,8 +547,10 @@ static int teo_select(struct cpuidle_dri * If there is a latency constraint, it may be necessary to select an * idle state shallower than the current candidate one. */ - if (idx > constraint_idx) + if (idx > constraint_idx) { idx = constraint_idx; + goto bail_out; + } /* * If the CPU is being utilized over the threshold, choose a shallower @@ -569,23 +571,35 @@ static int teo_select(struct cpuidle_dri end: /* - * Don't stop the tick if the selected state is a polling one or if the - * expected idle duration is shorter than the tick period length. + * Allow the tick to be stopped unless the selected state is a polling + * one or the expected idle duration is shorter than the tick period + * length. */ - if (((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) || - duration_ns < TICK_NSEC) && !tick_nohz_tick_stopped()) { - *stop_tick = false; + if ((!(drv->states[idx].flags & CPUIDLE_FLAG_POLLING) && + duration_ns >= TICK_NSEC) || tick_nohz_tick_stopped()) + return idx; - /* - * The tick is not going to be stopped, so if the target - * residency of the state to be returned is not within the time - * till the closest timer including the tick, try to correct - * that. - */ - if (idx > idx0 && - drv->states[idx].target_residency_ns > delta_tick) - idx = teo_find_shallower_state(drv, dev, idx, delta_tick, false); - } +retain_tick: + *stop_tick = false; + + /* + * The tick is not going to be stopped, so if the target residency of + * the state to be returned is not within the time till the closest + * timer including the tick, try to correct that. + */ + if (idx > idx0 && + drv->states[idx].target_residency_ns > delta_tick) + idx = teo_find_shallower_state(drv, dev, idx, delta_tick, false); + + return idx; + +bail_out: + /* + * Do not allow the tick to be stopped if the selected state is shallow + * enough. + */ + if (drv->states[idx].target_residency_ns < TICK_NSEC) + goto retain_tick; return idx; }
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