linux-kernel - [RFC PATCH 04/15] cpufreq: Fix the efficient idle check for Intel extended families

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Message-ID: <20241220213711.1892696-5-sohil.mehta@intel.com>
Date: Fri, 20 Dec 2024 21:36:59 +0000
From: Sohil Mehta <sohil.mehta@...el.com>
To: x86@...nel.org,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Tony Luck <tony.luck@...el.com>
Cc: Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Borislav Petkov <bp@...en8.de>,
	"H . Peter Anvin" <hpa@...or.com>,
	"Rafael J . Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>,
	Andy Lutomirski <luto@...nel.org>,
	Viresh Kumar <viresh.kumar@...aro.org>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Jean Delvare <jdelvare@...e.com>,
	Guenter Roeck <linux@...ck-us.net>,
	Sohil Mehta <sohil.mehta@...el.com>,
	Zhang Rui <rui.zhang@...el.com>,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-acpi@...r.kernel.org,
	linux-pm@...r.kernel.org,
	linux-hwmon@...r.kernel.org
Subject: [RFC PATCH 04/15] cpufreq: Fix the efficient idle check for Intel extended families

should_io_be_busy() only considers certain family 6 CPUs as having
efficient idling. However, Arjan (the original author) says that choice
was due to the lack of testing done on the old systems. He suggests to
consider all Intel processors as having efficient idle.

Extend the check to all processors starting with family 6.

Signed-off-by: Sohil Mehta <sohil.mehta@...el.com>
---
 drivers/cpufreq/cpufreq_ondemand.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index a7c38b8b3e78..dfafb161f1c4 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -15,6 +15,10 @@
 #include <linux/tick.h>
 #include <linux/sched/cpufreq.h>
 
+#ifdef CONFIG_X86
+#include <asm/cpu_device_id.h>
+#endif
+
 #include "cpufreq_ondemand.h"
 
 /* On-demand governor macros */
@@ -32,8 +36,7 @@ static unsigned int default_powersave_bias;
 /*
  * Not all CPUs want IO time to be accounted as busy; this depends on how
  * efficient idling at a higher frequency/voltage is.
- * Pavel Machek says this is not so for various generations of AMD and old
- * Intel systems.
+ * Pavel Machek says this is not so for various generations of AMD.
  * Mike Chan (android.com) claims this is also not true for ARM.
  * Because of this, whitelist specific known (series) of CPUs by default, and
  * leave all others up to the user.
@@ -42,11 +45,11 @@ static int should_io_be_busy(void)
 {
 #if defined(CONFIG_X86)
 	/*
-	 * For Intel, Core 2 (model 15) and later have an efficient idle.
+	 * Starting with Family 6 consider all Intel CPUs to have an
+	 * efficient idle.
 	 */
 	if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
-			boot_cpu_data.x86 == 6 &&
-			boot_cpu_data.x86_model >= 15)
+	    boot_cpu_data.x86_vfm >= INTEL_PENTIUM_PRO)
 		return 1;
 #endif
 	return 0;
-- 
2.43.0