From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 5B93E21D3F2; Mon, 26 Jan 2026 09:18:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769419096; cv=none; b=gAQV1xW6czjqn4zop6GmjMFwcseHSuPYJitp5fqLyexI5BS4pb0DOoxe9QUT7caSar+hMIW3DP+ob5j2eqsdEKCoLXfU6KFlKA45hVvCl2B5gEuUooRvBkJHldZsW/+rCiYa+IjKKDScD76OYwqlyvvyJRbTqR+RUGySo8TQymM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769419096; c=relaxed/simple; bh=rSJtuUW1nh61RobK6PZkWQD1UJcpgjBEU/vXCjYv+8o=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=JXAtFCVm0489+GVgBWn2vPyJF3AACdz33ZDtdGvZP6N6kE5lgsBynaFOv1Sc6yw6gDEop8Fez3DrdkA4g3GHDjLFFwbjDat0Ou+OudvlYGqDVW1uRehg/sl/fA4r7z1SBZjHw3hz6ZUH3Hk8FdY3/IPPELgEz2tX1PA4IoA5WwM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id BC9E5339; Mon, 26 Jan 2026 01:18:05 -0800 (PST) Received: from [10.1.32.17] (e127648.arm.com [10.1.32.17]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 5D60C3F632; Mon, 26 Jan 2026 01:18:11 -0800 (PST) Message-ID: <401cbcab-5a41-4aa2-97f8-3dccc069e836@arm.com> Date: Mon, 26 Jan 2026 09:18:09 +0000 Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 1/5] cpuidle: governors: teo: Avoid selecting states with zero-size bins To: "Rafael J. Wysocki" Cc: Linux PM , LKML , Doug Smythies References: <2257365.irdbgypaU6@rafael.j.wysocki> <3033265.e9J7NaK4W3@rafael.j.wysocki> <0d066ce0-b0bf-43f2-a1c4-56e5ac47cce1@arm.com> Content-Language: en-US From: Christian Loehle In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit On 1/23/26 20:46, Rafael J. Wysocki wrote: > On Wed, Jan 21, 2026 at 2:10 PM Christian Loehle > wrote: >> >> On 1/14/26 19:44, Rafael J. Wysocki wrote: >>> From: Rafael J. Wysocki >>> >>> If the last two enabled idle states have the same target residency which >>> is at least equal to TICK_NSET, teo may select the next-to-last one even >> >> s/TICK_NSET/TICK_NSEC > > Yup, thanks! > >>> though the size of that state's bin is 0, which is confusing. >>> >>> Prevent that from happening by adding a target residency check to the >>> relevant code path. >>> >>> Signed-off-by: Rafael J. Wysocki >>> --- >>> drivers/cpuidle/governors/teo.c | 10 ++++++++++ >>> 1 file changed, 10 insertions(+) >>> >>> --- a/drivers/cpuidle/governors/teo.c >>> +++ b/drivers/cpuidle/governors/teo.c >>> @@ -388,6 +388,15 @@ static int teo_select(struct cpuidle_dri >>> while (min_idx < idx && >>> drv->states[min_idx].target_residency_ns < TICK_NSEC) >>> min_idx++; >>> + >>> + /* >>> + * Avoid selecting a state with a lower index, but with >>> + * the same target residency as the current candidate >>> + * one. >>> + */ >>> + if (drv->states[min_idx].target_residency_ns == >>> + drv->states[idx].target_residency_ns) >> >> We need to check that min_idx isn't disabled though, otherwise we now skip a >> potential (enabled) idx==1 if min_idx==2 and min_idx is disabled. > > Not really because idx is the current candidate state and it is > enabled. We'll use idx if this check is true, not min_idx. > Are you sure? I meant initially: for (i = intercept_max_idx; i >= min_idx; i--) { intercept_sum += cpu_data->state_bins[i].intercepts; if (dev->states_usage[i].disable) continue; idx = i; if (2 * intercept_sum > idx_intercept_sum) break; } might skip an idx==3 if it enters with min_idx==2 (sorry, messed up the +-1 in the initial mail) even though idx==3 might have the same residency as idx==2. So if idx==2 is disabled we could've selected idx==3, but now won't and will go for idx==1 or whatever is the next shallower enabled state. Additionally an issue with this and patch 5/5: if (min_idx >= intercept_max_idx) { idx = min_idx; goto constraint; // CL: this will just select min_idx } will use min_idx even though it might be disabled and also the scenario I think we should just add something like ------8<------- cpuidle: teo: Fix intercept-logic selecting disabled Prevent min_idx to be set to a disabled state, which could lead to both a disabled state being returned by teo, but also an equally good state being skipped because it has a higher index than a disabled state. Signed-off-by: Christian Loehle --- drivers/cpuidle/governors/teo.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/drivers/cpuidle/governors/teo.c b/drivers/cpuidle/governors/teo.c index 4cf6302f99ad..94c5ef5df467 100644 --- a/drivers/cpuidle/governors/teo.c +++ b/drivers/cpuidle/governors/teo.c @@ -420,9 +420,11 @@ static int teo_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, * candidate one whose target residency is at least * equal to the tick period length. */ - while (min_idx < idx && - drv->states[min_idx].target_residency_ns < TICK_NSEC) - min_idx++; + while (i < idx && drv->states[i].target_residency_ns < TICK_NSEC) { + i++; + if (!dev->states_usage[i].disable) + min_idx = i; + } /* * Avoid selecting a state with a lower index, but with -- 2.34.1