5.15-stable review patch. If anyone has any objections, please let me know.
------------------
From: Rafael J. Wysocki rafael.j.wysocki@intel.com
[ Upstream commit fa3fa55de0d6177fdcaf6fc254f13cc8f33c3eed ]
Marc has reported that commit 85975daeaa4d ("cpuidle: menu: Avoid discarding useful information") caused the number of wakeup interrupts to increase on an idle system [1], which was not expected to happen after merely allowing shallower idle states to be selected by the governor in some cases.
However, on the system in question, all of the idle states deeper than WFI are rejected by the driver due to a firmware issue [2]. This causes the governor to only consider the recent interval duriation data corresponding to attempts to enter WFI that are successful and the recent invervals table is filled with values lower than the scheduler tick period. Consequently, the governor predicts an idle duration below the scheduler tick period length and avoids stopping the tick more often which leads to the observed symptom.
Address it by modifying the governor to update the recent intervals table also when entering the previously selected idle state fails, so it knows that the short idle intervals might have been the minority had the selected idle states been actually entered every time.
Fixes: 85975daeaa4d ("cpuidle: menu: Avoid discarding useful information") Link: https://lore.kernel.org/linux-pm/86o6sv6n94.wl-maz@kernel.org/ [1] Link: https://lore.kernel.org/linux-pm/7ffcb716-9a1b-48c2-aaa4-469d0df7c792@arm.co... [2] Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Tested-by: Christian Loehle christian.loehle@arm.com Tested-by: Marc Zyngier maz@kernel.org Reviewed-by: Christian Loehle christian.loehle@arm.com Link: https://patch.msgid.link/2793874.mvXUDI8C0e@rafael.j.wysocki Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/cpuidle/governors/menu.c | 21 +++++++++++++++++---- 1 file changed, 17 insertions(+), 4 deletions(-)
diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index e1e2721beb75..246b4a1b664a 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -158,6 +158,14 @@ static inline int performance_multiplier(unsigned int nr_iowaiters)
static DEFINE_PER_CPU(struct menu_device, menu_devices);
+static void menu_update_intervals(struct menu_device *data, unsigned int interval_us) +{ + /* Update the repeating-pattern data. */ + data->intervals[data->interval_ptr++] = interval_us; + if (data->interval_ptr >= INTERVALS) + data->interval_ptr = 0; +} + static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev);
/* @@ -288,6 +296,14 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, if (data->needs_update) { menu_update(drv, dev); data->needs_update = 0; + } else if (!dev->last_residency_ns) { + /* + * This happens when the driver rejects the previously selected + * idle state and returns an error, so update the recent + * intervals table to prevent invalid information from being + * used going forward. + */ + menu_update_intervals(data, UINT_MAX); }
/* determine the expected residency time, round up */ @@ -542,10 +558,7 @@ static void menu_update(struct cpuidle_driver *drv, struct cpuidle_device *dev)
data->correction_factor[data->bucket] = new_factor;
- /* update the repeating-pattern data */ - data->intervals[data->interval_ptr++] = ktime_to_us(measured_ns); - if (data->interval_ptr >= INTERVALS) - data->interval_ptr = 0; + menu_update_intervals(data, ktime_to_us(measured_ns)); }
/**