linux-kernel - [PATCH v4 3/3] x86: Print ratio freq_max/freq_base used in frequency invariance calculations

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Message-Id: <20201112182614.10700-4-ggherdovich@suse.cz>
Date:   Thu, 12 Nov 2020 19:26:14 +0100
From:   Giovanni Gherdovich <ggherdovich@...e.cz>
To:     Borislav Petkov <bp@...en8.de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Len Brown <lenb@...nel.org>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>
Cc:     Jon Grimm <Jon.Grimm@....com>,
        Nathan Fontenot <Nathan.Fontenot@....com>,
        Yazen Ghannam <Yazen.Ghannam@....com>,
        Thomas Lendacky <Thomas.Lendacky@....com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Pu Wen <puwen@...on.cn>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Doug Smythies <dsmythies@...us.net>, x86@...nel.org,
        linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org,
        Giovanni Gherdovich <ggherdovich@...e.cz>
Subject: [PATCH v4 3/3] x86: Print ratio freq_max/freq_base used in frequency invariance calculations

The value freq_max/freq_base is a fundamental component of frequency
invariance calculations. It may come from a variety of sources such as MSRs
or ACPI data, tracking it down when troubleshooting a system could be
non-trivial. It is worth saving it in the kernel logs.

 # dmesg | grep 'Estimated ratio of average max'
 [   14.024036] smpboot: Estimated ratio of average max frequency by base frequency (times 1024): 1289

Signed-off-by: Giovanni Gherdovich <ggherdovich@...e.cz>
---
 arch/x86/kernel/smpboot.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index c5dd5f6199d9..3577bb756d64 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -2110,6 +2110,7 @@ static void init_freq_invariance(bool secondary, bool cppc_ready)
 	if (ret) {
 		init_counter_refs();
 		static_branch_enable(&arch_scale_freq_key);
+		pr_info("Estimated ratio of average max frequency by base frequency (times 1024): %llu\n", arch_max_freq_ratio);
 	} else {
 		pr_debug("Couldn't determine max cpu frequency, necessary for scale-invariant accounting.\n");
 	}
-- 
2.26.2