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Groups > linux.kernel > #1261932
| From | riel@redhat.com |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH 1/3] cpuidle,x86: increase forced cut-off for polling to 20us |
| Date | 2015-11-03 23:40 +0100 |
| Message-ID | <qqSpc-nO-3@gated-at.bofh.it> (permalink) |
| References | <qqSpc-nO-5@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
From: Rik van Riel <riel@redhat.com> The cpuidle menu governor has a forced cut-off for polling at 5us, in order to deal with firmware that gives the OS bad information on cpuidle states, leading to the system spending way too much time in polling. However, at least one x86 CPU family (Atom) has chips that have a 20us break-even point for C1. Forcing the polling cut-off to less than that wastes performance and power. Increase the polling cut-off to 20us. Systems with a lower C1 latency will be found in the states table by the menu governor, which will pick those states as appropriate. Signed-off-by: Rik van Riel <riel@redhat.com> --- drivers/cpuidle/governors/menu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/menu.c index 22e4463d1787..ecc242a586c9 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -330,7 +330,7 @@ static int menu_select(struct cpuidle_driver *drv, struct cpuidle_device *dev) * We want to default to C1 (hlt), not to busy polling * unless the timer is happening really really soon. */ - if (data->next_timer_us > 5 && + if (data->next_timer_us > 20 && !drv->states[CPUIDLE_DRIVER_STATE_START].disabled && dev->states_usage[CPUIDLE_DRIVER_STATE_START].disable == 0) data->last_state_idx = CPUIDLE_DRIVER_STATE_START; -- 2.1.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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[PATCH 1/3] cpuidle,x86: increase forced cut-off for polling to 20us riel@redhat.com - 2015-11-03 23:40 +0100 Re: [PATCH 1/3] cpuidle,x86: increase forced cut-off for polling to 20us Arjan van de Ven <arjan@linux.intel.com> - 2015-11-04 17:10 +0100
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