From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6BA111170E for ; Mon, 11 Sep 2023 13:52:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id D98FEC433C8; Mon, 11 Sep 2023 13:52:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1694440374; bh=cALL11pxMCMbkkMlgSYOZevS+VGZLi48s8oi9YSpb6M=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cWgba850dL5+DPVYtcrKnL2/RW693UlBNu2M/2Gw5h+rwxwepOmCZwih7a/y0CWJN MLMGX/YY5tLVMoPquDqMFKRGGJcHtjCXmulTKWSKMBC3NX/pDt3OWQUkEZytTtTcWB NzAuIA86I10I7HJ46exg1inftMpCYSTvd3VctEe4= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, "Rafael J. Wysocki" , Sasha Levin , Kajetan Puchalski Subject: [PATCH 6.5 038/739] cpuidle: teo: Update idle duration estimate when choosing shallower state Date: Mon, 11 Sep 2023 15:37:17 +0200 Message-ID: <20230911134652.164667237@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20230911134650.921299741@linuxfoundation.org> References: <20230911134650.921299741@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.5-stable review patch. If anyone has any objections, please let me know. ------------------ From: Rafael J. Wysocki [ Upstream commit 3f0b0966b30982e843950b170b7a9ddfd8094428 ] The TEO governor takes CPU utilization into account by refining idle state selection when the utilization is above a certain threshold. This is done by choosing an idle state shallower than the previously selected one. However, when doing this, the idle duration estimate needs to be adjusted so as to prevent the scheduler tick from being stopped when the candidate idle state is shallow, which may lead to excessive energy usage if the CPU is not woken up quickly enough going forward. Moreover, if the scheduler tick has been stopped already and the new idle duration estimate is too small, the replacement candidate state cannot be used. Modify the relevant code to take the above observations into account. Fixes: 9ce0f7c4bc64 ("cpuidle: teo: Introduce util-awareness") Link: https://lore.kernel.org/linux-pm/CAJZ5v0jJxHj65r2HXBTd3wfbZtsg=_StzwO1kA5STDnaPe_dWA@mail.gmail.com Signed-off-by: Rafael J. Wysocki Reviewed-and-tested-by: Kajetan Puchalski Signed-off-by: Sasha Levin --- drivers/cpuidle/governors/teo.c | 40 ++++++++++++++++++++++++--------- 1 file changed, 30 insertions(+), 10 deletions(-) diff --git a/drivers/cpuidle/governors/teo.c b/drivers/cpuidle/governors/teo.c index 987fc5f3997dc..2cdc711679a5f 100644 --- a/drivers/cpuidle/governors/teo.c +++ b/drivers/cpuidle/governors/teo.c @@ -397,13 +397,23 @@ static int teo_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, * the shallowest non-polling state and exit. */ if (drv->state_count < 3 && cpu_data->utilized) { - for (i = 0; i < drv->state_count; ++i) { - if (!dev->states_usage[i].disable && - !(drv->states[i].flags & CPUIDLE_FLAG_POLLING)) { - idx = i; - goto end; - } - } + /* The CPU is utilized, so assume a short idle duration. */ + duration_ns = teo_middle_of_bin(0, drv); + /* + * If state 0 is enabled and it is not a polling one, select it + * right away unless the scheduler tick has been stopped, in + * which case care needs to be taken to leave the CPU in a deep + * enough state in case it is not woken up any time soon after + * all. If state 1 is disabled, though, state 0 must be used + * anyway. + */ + if ((!idx && !(drv->states[0].flags & CPUIDLE_FLAG_POLLING) && + teo_time_ok(duration_ns)) || dev->states_usage[1].disable) + idx = 0; + else /* Assume that state 1 is not a polling one and use it. */ + idx = 1; + + goto end; } /* @@ -539,10 +549,20 @@ static int teo_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, /* * If the CPU is being utilized over the threshold, choose a shallower - * non-polling state to improve latency + * non-polling state to improve latency, unless the scheduler tick has + * been stopped already and the shallower state's target residency is + * not sufficiently large. */ - if (cpu_data->utilized) - idx = teo_find_shallower_state(drv, dev, idx, duration_ns, true); + if (cpu_data->utilized) { + s64 span_ns; + + i = teo_find_shallower_state(drv, dev, idx, duration_ns, true); + span_ns = teo_middle_of_bin(i, drv); + if (teo_time_ok(span_ns)) { + idx = i; + duration_ns = span_ns; + } + } end: /* -- 2.40.1