From patchwork Mon Aug 12 12:42:26 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Rafael J. Wysocki" X-Patchwork-Id: 13760616 Received: from cloudserver094114.home.pl (cloudserver094114.home.pl [79.96.170.134]) (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 C4BB517C7B9; Mon, 12 Aug 2024 13:44:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=79.96.170.134 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723470285; cv=none; b=nyfTzmFLtZzJk3RqhtdeqNngWFQVcarphjFGBWZU6G4mew8c2qzfVEn7RZCzh3Fxt3D2h6kB8hHiBr5ba+DtEDFxEC+ARHft4e+up5zBBbRT92Ih5elxdnpvFlEn+YmabjsFw1YsRRQFQYvEzbIJbgW8Y34ZorjpIiEvesD+SK4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723470285; c=relaxed/simple; bh=iIufjcgGtpUjJVRP7Ol9ZIuMvVSgYnQutX7gorMPP7k=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=mD2bL9xvn+qVNs8a6SC3N6qwe5P/0Lkm3m5+JbuLQlpa52d99hgGwvupiDKmXwIEMpUnw1eLgpjTrkmBBlbVykJ5RYzOKFe7+sgCdBJHGd8gdEQ1jHuAhUyXrsgrVBQvOOqRO6h9VBWA86kzGaJHMqi7sJz8bXJqPIxeymt5qBw= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=rjwysocki.net; spf=pass smtp.mailfrom=rjwysocki.net; dkim=pass (2048-bit key) header.d=rjwysocki.net header.i=@rjwysocki.net header.b=PQ6R2FIh; arc=none smtp.client-ip=79.96.170.134 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=rjwysocki.net Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=rjwysocki.net Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=rjwysocki.net header.i=@rjwysocki.net header.b="PQ6R2FIh" Received: from localhost (127.0.0.1) (HELO v370.home.net.pl) by /usr/run/smtp (/usr/run/postfix/private/idea_relay_lmtp) via UNIX with SMTP (IdeaSmtpServer 6.2.0) id 5a12cf236ae3d380; Mon, 12 Aug 2024 14:44:42 +0200 Received: from kreacher.localnet (unknown [195.136.19.94]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by cloudserver094114.home.pl (Postfix) with ESMTPSA id 47A386F0D80; Mon, 12 Aug 2024 14:44:42 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=rjwysocki.net; s=dkim; t=1723466682; bh=iIufjcgGtpUjJVRP7Ol9ZIuMvVSgYnQutX7gorMPP7k=; h=From:Subject:Date; b=PQ6R2FIhkIP4vEfEfJMHDJsOaXRmbv5A+nsMbOAMgIS8g4j7hFczZSRpAQPdGXSca XiwkPz2+M1pYNrfbL6b7mkJl+JkifahSYfvIu1KlIPHDppzMzbCtAc/rTIjAjwmjya 49HluW3o3Muq7Jw4RbCuPBpd9VVivMm/CYjmVIlmUlSN1Ch4YNKPdnTWu+WDBXA/Oq ozZBFcsA+YMUOdTjg8buhziGbQ4ue+vHwacK3pUdlM2/jO348vML5aAfM0Lq27V5yi jKCaMfB77xeDq/9TA33ngUYnMWLNgb12dsIkJmEiFqItw9VTgf2tFrAPoZRf0oCXdN JUodnnvV60tbA== From: "Rafael J. Wysocki" To: x86 Maintainers Cc: LKML , Linux PM , Thomas Gleixner , Peter Zijlstra , Srinivas Pandruvada , "Rafael J. Wysocki" , Dietmar Eggemann , Ricardo Neri , Tim Chen Subject: [PATCH v2 2/3] x86/sched: Add basic support for CPU capacity scaling Date: Mon, 12 Aug 2024 14:42:26 +0200 Message-ID: <13573795.uLZWGnKmhe@rjwysocki.net> In-Reply-To: <4941491.31r3eYUQgx@rjwysocki.net> References: <4941491.31r3eYUQgx@rjwysocki.net> Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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: gggruggvucftvghtrhhoucdtuddrgeeftddruddttddgheehucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecujffqoffgrffnpdggtffipffknecuuegrihhlohhuthemucduhedtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpefhvfevufffkfgjfhgggfgtsehtufertddttdejnecuhfhrohhmpedftfgrfhgrvghlucflrdcuhgihshhotghkihdfuceorhhjfiesrhhjfiihshhotghkihdrnhgvtheqnecuggftrfgrthhtvghrnhepvdffueeitdfgvddtudegueejtdffteetgeefkeffvdeftddttdeuhfegfedvjefhnecukfhppeduleehrddufeeirdduledrleegnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehinhgvthepudelhedrudefiedrudelrdelgedphhgvlhhopehkrhgvrggthhgvrhdrlhhotggrlhhnvghtpdhmrghilhhfrhhomhepfdftrghfrggvlhculfdrucghhihsohgtkhhifdcuoehrjhifsehrjhifhihsohgtkhhirdhnvghtqedpnhgspghrtghpthhtohepuddtpdhrtghpthhtohepgiekieeskhgvrhhnvghlrdhorhhgpdhrtghpthhtoheplhhinhhugidqkhgvrhhnvghlsehvghgvrhdrkhgvrhhnvghlrdhorhhgpdhrtghpthhtoheplhhinhhugidqphhmsehvghgvrhdrkhgvrhhnvghlrdhorhhgpdhrtghpthhtohepthhglhigsehlihhnuhhtrhhonhhigidruggvpdhrtghpthhtohepphgvthgvrhiisehinhhfrhgruggvrggurdhorhhgpdhrtghpthhtohepshhrihhnihhvrghsrdhprghnughruhhvrggurgeslhhinhhugidrihhnthgvlhdrtghomhdprhgtphhtthhopehrrghfrggvlheskhgvrhhnvghlrdhorhhgpdhrtghpthhtohepughivghtmhgrrhdrvghgghgvmhgrnhhnsegrrhhmrdgtohhm X-DCC--Metrics: v370.home.net.pl 1024; Body=10 Fuz1=10 Fuz2=10 From: Rafael J. Wysocki In order be able to compute the sizes of tasks consistently across all CPUs in a hybrid system, it is necessary to provide CPU capacity scaling information to the scheduler via arch_scale_cpu_capacity(). Moreover, the value returned by arch_scale_freq_capacity() for the given CPU must correspond to the arch_scale_cpu_capacity() return value for it, or utilization computations will be inaccurate. Add support for it through per-CPU variables holding the capacity and maximum-to-base frequency ratio (times SCHED_CAPACITY_SCALE) that will be returned by arch_scale_cpu_capacity() and used by scale_freq_tick() to compute arch_freq_scale for the current CPU, respectively. In order to avoid adding measurable overhead for non-hybrid x86 systems, which are the vast majority in the field, whether or not the new hybrid CPU capacity scaling will be in effect is controlled by a static key. This static key is set by calling arch_enable_hybrid_capacity_scale() which also allocates memory for the per-CPU data and initializes it. Next, arch_set_cpu_capacity() is used to set the per-CPU variables mentioned above for each CPU and arch_rebuild_sched_domains() needs to be called for the scheduler to realize that capacity-aware scheduling can be used going forward. Signed-off-by: Rafael J. Wysocki --- v1 -> v2: * Allow arch_enable_hybrid_capacity_scale() to succeed when frequency- invariance is not enabled and do not disable capacity scaling in disable_freq_invariance_workfn() (it is not really necessary to do so and the code is simpler without doing that). Having done that, move arch_hybrid_cap_scale_key definition closer to the code using it. * Replace WARN_ON_ONCE() with WARN_ONCE() (2 places). * Fix arch_enable_hybrid_capacity_scale() return value when hybrid capacity scaling is already enabled. * Fix arch_set_cpu_capacity() kerneldoc comment. --- arch/x86/include/asm/topology.h | 13 +++++ arch/x86/kernel/cpu/aperfmperf.c | 87 ++++++++++++++++++++++++++++++++++++++- 2 files changed, 99 insertions(+), 1 deletion(-) Index: linux-pm/arch/x86/include/asm/topology.h =================================================================== --- linux-pm.orig/arch/x86/include/asm/topology.h +++ linux-pm/arch/x86/include/asm/topology.h @@ -280,11 +280,24 @@ static inline long arch_scale_freq_capac } #define arch_scale_freq_capacity arch_scale_freq_capacity +bool arch_enable_hybrid_capacity_scale(void); +void arch_set_cpu_capacity(int cpu, unsigned long cap, unsigned long base_cap, + unsigned long max_freq, unsigned long base_freq); + +unsigned long arch_scale_cpu_capacity(int cpu); +#define arch_scale_cpu_capacity arch_scale_cpu_capacity + extern void arch_set_max_freq_ratio(bool turbo_disabled); extern void freq_invariance_set_perf_ratio(u64 ratio, bool turbo_disabled); void arch_rebuild_sched_domains(void); #else +static inline bool arch_enable_hybrid_capacity_scale(void) { return false; } +static inline void arch_set_cpu_capacity(int cpu, unsigned long cap, + unsigned long base_cap, + unsigned long max_freq, + unsigned long base_freq) { } + static inline void arch_set_max_freq_ratio(bool turbo_disabled) { } static inline void freq_invariance_set_perf_ratio(u64 ratio, bool turbo_disabled) { } Index: linux-pm/arch/x86/kernel/cpu/aperfmperf.c =================================================================== --- linux-pm.orig/arch/x86/kernel/cpu/aperfmperf.c +++ linux-pm/arch/x86/kernel/cpu/aperfmperf.c @@ -349,9 +349,89 @@ static DECLARE_WORK(disable_freq_invaria DEFINE_PER_CPU(unsigned long, arch_freq_scale) = SCHED_CAPACITY_SCALE; EXPORT_PER_CPU_SYMBOL_GPL(arch_freq_scale); +static DEFINE_STATIC_KEY_FALSE(arch_hybrid_cap_scale_key); + +struct arch_hybrid_cpu_scale { + unsigned long capacity; + unsigned long freq_ratio; +}; + +static struct arch_hybrid_cpu_scale __percpu *arch_cpu_scale; + +/** + * arch_enable_hybrid_capacity_scale - Enable hybrid CPU capacity scaling + * + * Allocate memory for per-CPU data used by hybrid CPU capacity scaling, + * initialize it and set the static key controlling its code paths. + * + * Must be called before arch_set_cpu_capacity(). + */ +bool arch_enable_hybrid_capacity_scale(void) +{ + int cpu; + + if (static_branch_unlikely(&arch_hybrid_cap_scale_key)) { + WARN_ONCE(1, "Hybrid CPU capacity scaling already enabled"); + return true; + } + arch_cpu_scale = alloc_percpu(struct arch_hybrid_cpu_scale); + if (!arch_cpu_scale) + return false; + + for_each_possible_cpu(cpu) { + per_cpu_ptr(arch_cpu_scale, cpu)->capacity = SCHED_CAPACITY_SCALE; + per_cpu_ptr(arch_cpu_scale, cpu)->freq_ratio = arch_max_freq_ratio; + } + + static_branch_enable(&arch_hybrid_cap_scale_key); + + pr_info("Hybrid CPU capacity scaling enabled\n"); + + return true; +} + +/** + * arch_set_cpu_capacity - Set scale-invariance parameters for a CPU + * @cpu: Target CPU. + * @cap: Capacity of @cpu, relative to @base_cap, at its maximum frequency. + * @base_cap: System-wide maximum CPU capacity. + * @max_freq: Frequency of @cpu corresponding to @cap. + * @base_freq: Frequency of @cpu at which MPERF counts. + * + * The units in which @cap and @base_cap are expressed do not matter, so long + * as they are consistent, because the former is effectively divided by the + * latter. Analogously for @max_freq and @base_freq. + * + * After calling this function for all CPUs, call arch_rebuild_sched_domains() + * to let the scheduler know that capacity-aware scheduling can be used going + * forward. + */ +void arch_set_cpu_capacity(int cpu, unsigned long cap, unsigned long base_cap, + unsigned long max_freq, unsigned long base_freq) +{ + if (static_branch_likely(&arch_hybrid_cap_scale_key)) { + WRITE_ONCE(per_cpu_ptr(arch_cpu_scale, cpu)->capacity, + div_u64(cap << SCHED_CAPACITY_SHIFT, base_cap)); + WRITE_ONCE(per_cpu_ptr(arch_cpu_scale, cpu)->freq_ratio, + div_u64(max_freq << SCHED_CAPACITY_SHIFT, base_freq)); + } else { + WARN_ONCE(1, "Hybrid CPU capacity scaling not enabled"); + } +} + +unsigned long arch_scale_cpu_capacity(int cpu) +{ + if (static_branch_unlikely(&arch_hybrid_cap_scale_key)) + return READ_ONCE(per_cpu_ptr(arch_cpu_scale, cpu)->capacity); + + return SCHED_CAPACITY_SCALE; +} +EXPORT_SYMBOL_GPL(arch_scale_cpu_capacity); + static void scale_freq_tick(u64 acnt, u64 mcnt) { u64 freq_scale; + u64 freq_ratio; if (!arch_scale_freq_invariant()) return; @@ -359,7 +439,12 @@ static void scale_freq_tick(u64 acnt, u6 if (check_shl_overflow(acnt, 2*SCHED_CAPACITY_SHIFT, &acnt)) goto error; - if (check_mul_overflow(mcnt, arch_max_freq_ratio, &mcnt) || !mcnt) + if (static_branch_unlikely(&arch_hybrid_cap_scale_key)) + freq_ratio = READ_ONCE(this_cpu_ptr(arch_cpu_scale)->freq_ratio); + else + freq_ratio = arch_max_freq_ratio; + + if (check_mul_overflow(mcnt, freq_ratio, &mcnt) || !mcnt) goto error; freq_scale = div64_u64(acnt, mcnt);