linux-kernel - [tip: sched/core] x86: Print ratio freq_max/freq_base used in frequency invariance calculations

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Date:   Thu, 03 Dec 2020 09:13:20 -0000
From:   "tip-bot2 for Giovanni Gherdovich" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Giovanni Gherdovich <ggherdovich@...e.cz>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: sched/core] x86: Print ratio freq_max/freq_base used in
 frequency invariance calculations

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     24f326686c925a848d603a2c22f1f6ed1b7786e2
Gitweb:        https://git.kernel.org/tip/24f326686c925a848d603a2c22f1f6ed1b7786e2
Author:        Giovanni Gherdovich <ggherdovich@...e.cz>
AuthorDate:    Thu, 12 Nov 2020 19:26:14 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Thu, 03 Dec 2020 10:00:35 +01:00

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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/20201112182614.10700-4-ggherdovich@suse.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 c5dd5f6..3577bb7 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");
 	}