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(host81-157-90-255.range81-157.btcentralplus.com. [81.157.90.255]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-36d27193339sm3466071f8f.63.2024.08.08.16.44.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Aug 2024 16:44:18 -0700 (PDT) From: Qais Yousef To: Ingo Molnar , Peter Zijlstra , "Rafael J. Wysocki" , Viresh Kumar , Vincent Guittot , Dietmar Eggemann Cc: linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, Qais Yousef Subject: [PATCH v3] sched: cpufreq: Rename map_util_perf to sugov_apply_dvfs_headroom Date: Fri, 9 Aug 2024 00:44:15 +0100 Message-Id: <20240808234415.554937-1-qyousef@layalina.io> 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 We are providing headroom for the utilization to grow until the next decision point to pick the next frequency. Give the function a better name and give it some documentation. It is not really mapping anything. Also move it to cpufreq_schedutil.c. This function relies on updating util signal appropriately to give a headroom to grow. This is tied to schedutil and scheduler and not something that can be shared with other governors. Acked-by: Viresh Kumar Acked-by: Rafael J. Wysocki Reviewed-by: Vincent Guittot Signed-off-by: Qais Yousef Reviewed-by: Christian Loehle --- Changes in v3: 1. Add Reviewed-by from Vincent Changes in v2: 1. Add Acked-by from Viresh and Raphael (Thanks!) 2. Move the function to cpufreq_schedutil.c instead of sched.h 3. Name space the function with sugov_ to indicate it is special to this governor only and not generic. include/linux/sched/cpufreq.h | 5 ----- kernel/sched/cpufreq_schedutil.c | 20 +++++++++++++++++++- 2 files changed, 19 insertions(+), 6 deletions(-) diff --git a/include/linux/sched/cpufreq.h b/include/linux/sched/cpufreq.h index bdd31ab93bc5..d01755d3142f 100644 --- a/include/linux/sched/cpufreq.h +++ b/include/linux/sched/cpufreq.h @@ -28,11 +28,6 @@ static inline unsigned long map_util_freq(unsigned long util, { return freq * util / cap; } - -static inline unsigned long map_util_perf(unsigned long util) -{ - return util + (util >> 2); -} #endif /* CONFIG_CPU_FREQ */ #endif /* _LINUX_SCHED_CPUFREQ_H */ diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index eece6244f9d2..575df3599813 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -178,12 +178,30 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy, return cpufreq_driver_resolve_freq(policy, freq); } +/* + * DVFS decision are made at discrete points. If CPU stays busy, the util will + * continue to grow, which means it could need to run at a higher frequency + * before the next decision point was reached. IOW, we can't follow the util as + * it grows immediately, but there's a delay before we issue a request to go to + * higher frequency. The headroom caters for this delay so the system continues + * to run at adequate performance point. + * + * This function provides enough headroom to provide adequate performance + * assuming the CPU continues to be busy. + * + * At the moment it is a constant multiplication with 1.25. + */ +static inline unsigned long sugov_apply_dvfs_headroom(unsigned long util) +{ + return util + (util >> 2); +} + unsigned long sugov_effective_cpu_perf(int cpu, unsigned long actual, unsigned long min, unsigned long max) { /* Add dvfs headroom to actual utilization */ - actual = map_util_perf(actual); + actual = sugov_apply_dvfs_headroom(actual); /* Actually we don't need to target the max performance */ if (actual < max) max = actual;