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cpuidle: governors: menu: Select polling state in some more cases

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A throughput regression of 11% introduced by commit 779b1a1cb1 ("cpuidle:
governors: menu: Avoid selecting states with too much latency") has been
reported and it is related to the case when the menu governor checks if
selecting a proper idle state instead of a polling one makes sense.

In particular, it is questionable to do so if the exit latency of the
idle state in question exceeds the predicted idle duration, so add a
check for that, which is sufficient to make the reported regression go
away, and update the related code comment accordingly.

Fixes: 779b1a1cb1 ("cpuidle: governors: menu: Avoid selecting states with too much latency")
Closes: https://lore.kernel.org/linux-pm/004501dc43c9$ec8aa930$c59ffb90$@telus.net/
Reported-by: Doug Smythies <dsmythies@telus.net>
Tested-by: Doug Smythies <dsmythies@telus.net>
Cc: All applicable <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/12786727.O9o76ZdvQC@rafael.j.wysocki
This commit is contained in:
Rafael J. Wysocki
2025-10-23 19:12:57 +02:00
parent dcb6fa37fd
commit db86f55bf8
1 changed files with 5 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
drivers/cpuidle/governors/menu.c
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@@ -318,10 +318,13 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev,
/* /*
* Use a physical idle state, not busy polling, unless a timer * Use a physical idle state, not busy polling, unless a timer
* is going to trigger soon enough. * is going to trigger soon enough or the exit latency of the
* idle state in question is greater than the predicted idle
* duration.
*/ */
if ((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) && if ((drv->states[idx].flags & CPUIDLE_FLAG_POLLING) &&
s->target_residency_ns <= data->next_timer_ns) { s->target_residency_ns <= data->next_timer_ns &&
s->exit_latency_ns <= predicted_ns) {
predicted_ns = s->target_residency_ns; predicted_ns = s->target_residency_ns;
idx = i; idx = i;
break; break;