linux-kernel - [tip: x86/cleanups] x86/aperfmperf: Store aperf/mperf data for cpu frequency reads

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Date:   Wed, 27 Apr 2022 13:56:07 -0000
From:   "tip-bot2 for Thomas Gleixner" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: x86/cleanups] x86/aperfmperf: Store aperf/mperf data for cpu
 frequency reads

The following commit has been merged into the x86/cleanups branch of tip:

Commit-ID:     3b1fc17f635164d74934f67d3bb46cdf877fb67f
Gitweb:        https://git.kernel.org/tip/3b1fc17f635164d74934f67d3bb46cdf877fb67f
Author:        Thomas Gleixner <tglx@...utronix.de>
AuthorDate:    Fri, 15 Apr 2022 21:20:01 +02:00
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Wed, 27 Apr 2022 15:51:08 +02:00

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>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Acked-by: Paul E. McKenney <paulmck@...nel.org>
Link: https://lore.kernel.org/r/20220415161206.817702355@linutronix.de

---
 arch/x86/kernel/cpu/aperfmperf.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/aperfmperf.c b/arch/x86/kernel/cpu/aperfmperf.c
index df528a4..963c069 100644
--- 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);
 }