linux-kernel - [PATCH 4/5] intel_pstate: skip scheduler hook when in "performance" mode.

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Message-Id: <1ecfadf4193fbd8873d4bcda9e9faec5825bcafb.1496889051.git.len.brown@intel.com>
Date:   Wed,  7 Jun 2017 19:39:15 -0700
From:   Len Brown <lenb@...nel.org>
To:     x86@...nel.org, srinivas.pandruvada@...ux.intel.com,
        hpa@...ux.intel.com, peterz@...radead.org, rafael@...nel.org
Cc:     linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Len Brown <len.brown@...el.com>
Subject: [PATCH 4/5] intel_pstate: skip scheduler hook when in "performance" mode.

From: Len Brown <len.brown@...el.com>

When the governor is set to "performance", intel_pstate does not
need the scheduler hook for doing any calculations.  Under these
conditions, its only purpose is to continue to maintain
cpufreq/scaling_cur_freq.

But the cpufreq/scaling_cur_freq sysfs attribute is now provided by
the x86 cpufreq core on all modern x86 systems, including
all systems supported by the intel_pstate driver.

So in "performance" governor mode, the scheduler hook can be skipped.
This applies to both in Software and Hardware P-state control modes.

Suggested-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Signed-off-by: Len Brown <len.brown@...el.com>
---
 drivers/cpufreq/intel_pstate.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index 5d67780..0ff3a4b 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2025,10 +2025,10 @@ static int intel_pstate_set_policy(struct cpufreq_policy *policy)
 		 */
 		intel_pstate_clear_update_util_hook(policy->cpu);
 		intel_pstate_max_within_limits(cpu);
+	} else {
+		intel_pstate_set_update_util_hook(policy->cpu);
 	}
 
-	intel_pstate_set_update_util_hook(policy->cpu);
-
 	if (hwp_active)
 		intel_pstate_hwp_set(policy->cpu);
 
-- 
2.7.4