Path: csiph.com!fu-berlin.de!bofh.it!news.nic.it!robomod
From: Len Brown <lenb@kernel.org>
Newsgroups: linux.kernel
Subject: [PATCH 4/4] intel_pstate: skip scheduler hook when in "performance" mode.
Date: Sat, 24 Jun 2017 07:20:01 +0200
Message-ID: <tVLEd-3Fl-1@gated-at.bofh.it>
References: <tVLEd-3Fl-3@gated-at.bofh.it>
Reply-To: Len Brown <lenb@kernel.org>
Organization: Intel Open Source Technology Center
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From: Len Brown <len.brown@intel.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.

The cpufreq/scaling_cur_freq sysfs attribute is now provided by
shared x86 cpufreq code on 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@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.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 4ec5668..4538182 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -2031,10 +2031,10 @@ 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