From patchwork Thu Jun 6 09:00:44 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Loehle X-Patchwork-Id: 13688076 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 532B613D2A0; Thu, 6 Jun 2024 09:01:06 +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=1717664469; cv=none; b=h/c4RJrK3kwR8Dt8Blv+2ccSSjzLIKxOKCwSIKxxLSMONmXQBAjhI7q2XCG7LR98U/R/5U45aYGwADivq1mltpfOSsARgBY6WyuPjE2g4FKCLQXdqQ7xK/EdxuUGRt0Skn/e5/siKKshhGA5VTawXIPzvmMJEpEcaVdbG7Kmy4g= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717664469; c=relaxed/simple; bh=NiTOBUGn2SHNFF6K2VUokZnP4aqmxRiJ4zI2bmjUAcc=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=cQHrASelhiXtn2UD98m/el3KflD4LjVBcQ/Q7OR36bTTMwd3BsZP296XN1E6JhOaOsR9rXG6vZmBHn08GCT6WsueyXEOnvSlg3erdkZ5XccExnLyl5mPxhspBUGz3M0e8FtlmlZ3/VrMj+vS4192mHIdzpUZw4YHaG3HtksQgEs= 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 C014A339; Thu, 6 Jun 2024 02:01:29 -0700 (PDT) Received: from e127648.arm.com (unknown [10.57.71.137]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPA id DCA993F762; Thu, 6 Jun 2024 02:01:02 -0700 (PDT) From: Christian Loehle To: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, rafael@kernel.org Cc: vincent.guittot@linaro.org, qyousef@layalina.io, peterz@infradead.org, daniel.lezcano@linaro.org, anna-maria@linutronix.de, kajetan.puchalski@arm.com, lukasz.luba@arm.com, dietmar.eggemann@arm.com, Christian Loehle Subject: [PATCH 0/6] cpuidle: teo: fixes and improvements Date: Thu, 6 Jun 2024 10:00:44 +0100 Message-Id: <20240606090050.327614-1-christian.loehle@arm.com> X-Mailer: git-send-email 2.34.1 Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Hi all, so my investigation into teo lead to the following fixes and improvements. Logically they are mostly independent, that's why this cover letter is quite short, details are in the patches. 1/6: As discussed, the utilization threshold is too high, while there are benefits in certain workloads, there are quite a few regressions, too. 2/6: Especially with the new util threshold, stopping tick makes little sense when utilized is detected, so don't. 3/6: Particularly with WFI, even if it's the only state, stopping the tick has benefits, so enable that in the early bail out. 4/6: Stopping the tick with 0 cost (if the idle state dictates it) is too aggressive IMO, so add 1ms constant cost. XXX: This has the issue of now being counted as idle_miss, so we could consider adding this to the states, too, but the simple implementation of this would have the downside that the cost is added to deeper states even if the tick is already off. 5/6: Remove the 'recent' intercept logic, see my findings in: https://lore.kernel.org/lkml/0ce2d536-1125-4df8-9a5b-0d5e389cd8af@arm.com/ I haven't found a way to salvage this properly, so I removed it. The regular intercept seems to decay fast enough to not need this, but we could change it if that turns out to be the case. 6/6: The rest of the intercept logic had issues, too. See the commit. TODO: add some measurements of common workloads and some simple sanity tests (like Vincent described in low utilization workloads if the state selection looks reasonable). I have some, but more (and more standardized) would be beneficial. Happy for anyone to take a look and test as well. Some numbers for context: Maybe some numbers for context, I'll probably add them to the cover letter. Comparing: - IO workload (intercept heavy). - Timer workload very low utilization (check for deepest state) - hackbench (high utilization) all on RK3399 with CONFIG_HZ=100. target_residencies: 1, 900, 2000 1. IO workload, 5 runs, results sorted, in read IOPS. fio --minimal --time_based --name=fiotest --filename=/dev/nvme0n1 --runtime=30 --rw=randread --bs=4k --ioengine=psync --iodepth=1 --direct=1 | cut -d \; -f 8; teo fixed: /dev/nvme0n1 [4597, 4673, 4727, 4741, 4756] /dev/mmcblk2 [5753, 5832, 5837, 5911, 5949] /dev/mmcblk1 [2059, 2062, 2070, 2071, 2080] teo mainline: /dev/nvme0n1 [3793, 3825, 3846, 3865, 3964] /dev/mmcblk2 [3831, 4110, 4154, 4203, 4228] /dev/mmcblk1 [1559, 1564, 1596, 1611, 1618] menu: /dev/nvme0n1 [2571, 2630, 2804, 2813, 2917] /dev/mmcblk2 [4181, 4260, 5062, 5260, 5329] /dev/mmcblk1 [1567, 1581, 1585, 1603, 1769] 2. Timer workload (through IO for my convenience ;) ) Results in read IOPS, fio same as above. echo "0 2097152 zero" | dmsetup create dm-zeros echo "0 2097152 delay /dev/mapper/dm-zeros 0 50" | dmsetup create dm-slow (Each IO is delayed by timer of 50ms, should be mostly in state2) teo fixed: 3269 cpu_idle total 48 cpu_idle_miss 30 cpu_idle_miss above 18 cpu_idle_miss below teo mainline: 3221 cpu_idle total 1269 cpu_idle_miss 22 cpu_idle_miss above 1247 cpu_idle_miss below menu: 3433 cpu_idle total 114 cpu_idle_miss 61 cpu_idle_miss above 53 cpu_idle_miss below Residencies: teo mainline isn't in state2 at all, teo fixed is more in state2 than menu, but both are >95%. tldr: overall teo fixed spends more time in state2 while having fewer idle_miss than menu. teo mainline was just way too aggressive at selecting shallow states. 3. Hackbench, 5 runs for i in $(seq 0 4); do hackbench -l 100 -g 100 ; sleep 1; done teo fixed: Time: 4.807 Time: 4.856 Time: 5.072 Time: 4.934 Time: 4.962 teo mainline: Time: 4.945 Time: 5.021 Time: 4.927 Time: 4.923 Time: 5.137 menu: Time: 4.991 Time: 4.884 Time: 4.880 Time: 4.946 Time: 4.980 tldr: all comparable, teo mainline slightly worse Kind Regards, Christian Christian Loehle (6): cpuidle: teo: Increase util-threshold cpuidle: teo: Don't stop tick on utilized cpuidle: teo: Don't always stop tick on one state cpuidle: teo: Increase minimum time to stop tick cpuidle: teo: Remove recent intercepts metric cpuidle: teo: Don't count non-existent intercepts drivers/cpuidle/governors/teo.c | 121 +++++++++++++------------------- 1 file changed, 48 insertions(+), 73 deletions(-) --- 2.34.1