From nobody Wed Dec 17 08:11:58 2025 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E87A8E743F8 for ; Fri, 29 Sep 2023 08:39:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232930AbjI2Ijh (ORCPT ); Fri, 29 Sep 2023 04:39:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34748 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232971AbjI2IjO (ORCPT ); Fri, 29 Sep 2023 04:39:14 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 81CF7CD3; Fri, 29 Sep 2023 01:39:04 -0700 (PDT) Date: Fri, 29 Sep 2023 08:39:02 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1695976743; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=VleefmjdcCp/KazIv8mxgFWlfnF4dtOyZiY7hzPqcss=; b=oE5J5Ihfbv63Jgncqr/0F8k73BaSYgdTcU+V0pQzzA/PG80z5HUrLHi/nm7+cx6cvwelUa icW8Y5chHC4rlltfyMg8UL1baJbuZUFZ74NUYsvNz1x++7M82Ai8XodcxVwiRGzwol9GtJ R+1/PWguxWs+3KDViDx3/4aKegu9gskrh4I2dZXtjH2QI4tc8a4ktZ9+Y+BiSf1JbttgtU FJm6UmszTINFV913sKETo0fydFEEdIWa98RkztCUkNuKwNnOtbzSztSITGdha/Y+PXfFPh LRbR2A/a7d0uRDVdalFEMS4BAUgLKuzN36gqBUk52btn89rGI6IQgWvnFmLHsQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1695976743; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=VleefmjdcCp/KazIv8mxgFWlfnF4dtOyZiY7hzPqcss=; b=vzFEz38cCWuZ4Ujq1Vki7a1HnKp+WRZWYvARZE/uk52+QD7/fZIR/j6oKfeTheSEOnPKWe tgmmy7HYVvLBMLCg== From: "tip-bot2 for Qais Yousef" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: sched/core] sched/uclamp: Set max_spare_cap_cpu even if max_spare_cap is 0 Cc: "Qais Yousef (Google)" , Ingo Molnar , Vincent Guittot , Dietmar Eggemann , "Peter Zijlstra (Intel)" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20230916232955.2099394-2-qyousef@layalina.io> References: <20230916232955.2099394-2-qyousef@layalina.io> MIME-Version: 1.0 Message-ID: <169597674244.27769.17215104305593460514.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The following commit has been merged into the sched/core branch of tip: Commit-ID: 6b00a40147653c8ea748e8f4396510f252763364 Gitweb: https://git.kernel.org/tip/6b00a40147653c8ea748e8f4396510f25= 2763364 Author: Qais Yousef AuthorDate: Sun, 17 Sep 2023 00:29:53 +01:00 Committer: Ingo Molnar CommitterDate: Fri, 29 Sep 2023 10:29:14 +02:00 sched/uclamp: Set max_spare_cap_cpu even if max_spare_cap is 0 When uclamp_max is being used, the util of the task could be higher than the spare capacity of the CPU, but due to uclamp_max value we force-fit it there. The way the condition for checking for max_spare_cap in find_energy_efficient_cpu() was constructed; it ignored any CPU that has its spare_cap less than or _equal_ to max_spare_cap. Since we initialize max_spare_cap to 0; this lead to never setting max_spare_cap_cpu and hence ending up never performing compute_energy() for this cluster and missing an opportunity for a better energy efficient placement to honour uclamp_max setting. max_spare_cap =3D 0; cpu_cap =3D capacity_of(cpu) - cpu_util(p); // 0 if cpu_util(p) is high ... util_fits_cpu(...); // will return true if uclamp_max forces it to fit ... // this logic will fail to update max_spare_cap_cpu if cpu_cap is 0 if (cpu_cap > max_spare_cap) { max_spare_cap =3D cpu_cap; max_spare_cap_cpu =3D cpu; } prev_spare_cap suffers from a similar problem. Fix the logic by converting the variables into long and treating -1 value as 'not populated' instead of 0 which is a viable and correct spare capacity value. We need to be careful signed comparison is used when comparing with cpu_cap in one of the conditions. Fixes: 1d42509e475c ("sched/fair: Make EAS wakeup placement consider uclamp= restrictions") Signed-off-by: Qais Yousef (Google) Signed-off-by: Ingo Molnar Reviewed-by: Vincent Guittot Reviewed-by: Dietmar Eggemann Acked-by: Peter Zijlstra (Intel) Link: https://lore.kernel.org/r/20230916232955.2099394-2-qyousef@layalina.io --- kernel/sched/fair.c | 11 +++++------ 1 file changed, 5 insertions(+), 6 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 2973173..4ce949b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7703,11 +7703,10 @@ static int find_energy_efficient_cpu(struct task_st= ruct *p, int prev_cpu) for (; pd; pd =3D pd->next) { unsigned long util_min =3D p_util_min, util_max =3D p_util_max; unsigned long cpu_cap, cpu_thermal_cap, util; - unsigned long cur_delta, max_spare_cap =3D 0; + long prev_spare_cap =3D -1, max_spare_cap =3D -1; unsigned long rq_util_min, rq_util_max; - unsigned long prev_spare_cap =3D 0; + unsigned long cur_delta, base_energy; int max_spare_cap_cpu =3D -1; - unsigned long base_energy; int fits, max_fits =3D -1; =20 cpumask_and(cpus, perf_domain_span(pd), cpu_online_mask); @@ -7770,7 +7769,7 @@ static int find_energy_efficient_cpu(struct task_stru= ct *p, int prev_cpu) prev_spare_cap =3D cpu_cap; prev_fits =3D fits; } else if ((fits > max_fits) || - ((fits =3D=3D max_fits) && (cpu_cap > max_spare_cap))) { + ((fits =3D=3D max_fits) && ((long)cpu_cap > max_spare_cap))) { /* * Find the CPU with the maximum spare capacity * among the remaining CPUs in the performance @@ -7782,7 +7781,7 @@ static int find_energy_efficient_cpu(struct task_stru= ct *p, int prev_cpu) } } =20 - if (max_spare_cap_cpu < 0 && prev_spare_cap =3D=3D 0) + if (max_spare_cap_cpu < 0 && prev_spare_cap < 0) continue; =20 eenv_pd_busy_time(&eenv, cpus, p); @@ -7790,7 +7789,7 @@ static int find_energy_efficient_cpu(struct task_stru= ct *p, int prev_cpu) base_energy =3D compute_energy(&eenv, pd, cpus, p, -1); =20 /* Evaluate the energy impact of using prev_cpu. */ - if (prev_spare_cap > 0) { + if (prev_spare_cap > -1) { prev_delta =3D compute_energy(&eenv, pd, cpus, p, prev_cpu); /* CPU utilization has changed */