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Wysocki" To: Linux PM Cc: LKML , Peter Zijlstra , Anna-Maria Behnsen , Frederic Weisbecker , Kajetan Puchalski Subject: [PATCH v3 1/3] cpuidle: teo: Update idle duration estimate when choosing shallower state Date: Mon, 31 Jul 2023 20:56:35 +0200 Message-ID: <13332551.uLZWGnKmhe@kreacher> In-Reply-To: <4515817.LvFx2qVVIh@kreacher> References: <4515817.LvFx2qVVIh@kreacher> MIME-Version: 1.0 X-CLIENT-IP: 195.136.19.94 X-CLIENT-HOSTNAME: 195.136.19.94 X-VADE-SPAMSTATE: clean X-VADE-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgedviedrjeeggddutdekucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecujffqoffgrffnpdggtffipffknecuuegrihhlohhuthemucduhedtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpefhvfevufffkfgjfhgggfgtsehtufertddttdejnecuhfhrohhmpedftfgrfhgrvghlucflrdcuhgihshhotghkihdfuceorhhjfiesrhhjfiihshhotghkihdrnhgvtheqnecuggftrfgrthhtvghrnhepfeduudeutdeugfelffduieegiedtueefledvjeegffdttefhhffhtefhleejgfetnecuffhomhgrihhnpehkvghrnhgvlhdrohhrghenucfkphepudelhedrudefiedrudelrdelgeenucevlhhushhtvghrufhiiigvpedtnecurfgrrhgrmhepihhnvghtpeduleehrddufeeirdduledrleegpdhhvghlohepkhhrvggrtghhvghrrdhlohgtrghlnhgvthdpmhgrihhlfhhrohhmpedftfgrfhgrvghlucflrdcuhgihshhotghkihdfuceorhhjfiesrhhjfiihshhotghkihdrnhgvtheqpdhnsggprhgtphhtthhopeeipdhrtghpthhtoheplhhinhhugidqphhmsehvghgvrhdrkhgvrhhnvghlrdhorhhgpdhrtghpthhtoheplhhinhhugidqkhgvrhhnvghlsehvghgvrhdrkhgvrhhnvghlrdhorhhgpdhrtghpthhtohepphgvthgvrhiisehinhhfrhgruggvrggurdhorhhgpdhrtghpthhtoheprghnnhgrqdhmrghrihgrsehlihhnuhht rhhonhhigidruggvpdhrtghpthhtohepfhhrvgguvghrihgtsehkvghrnhgvlhdrohhrghdprhgtphhtthhopehkrghjvghtrghnrdhpuhgthhgrlhhskhhisegrrhhmrdgtohhm X-DCC--Metrics: v370.home.net.pl 1024; Body=6 Fuz1=6 Fuz2=6 X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00,SPF_HELO_NONE, SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1772966017608913394 X-GMAIL-MSGID: 1772966017608913394 From: Rafael J. Wysocki 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 --- v2 -> v3: * Make the handling of the "2 idle state and utilized CPU" case more straightforward. v1 -> v2: * Rework the code handling the special case when the CPU is utilized and there are only 2 idle states (drop the loop, avoid using state 0 when the tick has been stopped already and it is too shallow, check if state 1 is not disabled when about to use it, set low idle duration estimate). * Changelog edits. --- drivers/cpuidle/governors/teo.c | 40 ++++++++++++++++++++++++++++++---------- 1 file changed, 30 insertions(+), 10 deletions(-) Index: linux-pm/drivers/cpuidle/governors/teo.c =================================================================== --- linux-pm.orig/drivers/cpuidle/governors/teo.c +++ linux-pm/drivers/cpuidle/governors/teo.c @@ -397,13 +397,23 @@ static int teo_select(struct cpuidle_dri * 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_dri /* * 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: /*