linux-kernel - [patch 08/10] x86/aperfmperf: Store aperf/mperf data for cpu frequency reads

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Date:   Fri, 15 Apr 2022 21:20:01 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-pm@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        "Paul E. McKenney" <paulmck@...nel.org>
Subject: [patch 08/10] x86/aperfmperf: Store aperf/mperf data for cpu frequency reads

Now that the MSR readout is unconditional, store the results in the per CPU
data structure along with a jiffies timestamp for the CPU frequency readout
code.

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
---
 arch/x86/kernel/cpu/aperfmperf.c |   14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

--- a/arch/x86/kernel/cpu/aperfmperf.c
+++ b/arch/x86/kernel/cpu/aperfmperf.c
@@ -24,11 +24,17 @@
 #include "cpu.h"
 
 struct aperfmperf {
+	seqcount_t	seq;
+	unsigned long	last_update;
+	u64		acnt;
+	u64		mcnt;
 	u64		aperf;
 	u64		mperf;
 };
 
-static DEFINE_PER_CPU_SHARED_ALIGNED(struct aperfmperf, cpu_samples);
+static DEFINE_PER_CPU_SHARED_ALIGNED(struct aperfmperf, cpu_samples) = {
+	.seq = SEQCNT_ZERO(cpu_samples.seq)
+};
 
 struct aperfmperf_sample {
 	unsigned int	khz;
@@ -515,6 +521,12 @@ void arch_scale_freq_tick(void)
 	s->aperf = aperf;
 	s->mperf = mperf;
 
+	raw_write_seqcount_begin(&s->seq);
+	s->last_update = jiffies;
+	s->acnt = acnt;
+	s->mcnt = mcnt;
+	raw_write_seqcount_end(&s->seq);
+
 	scale_freq_tick(acnt, mcnt);
 }