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Message-ID: <20160926090557.GA29668@suselix.suse.de>
Date: Mon, 26 Sep 2016 11:05:57 +0200
From: Andreas Herrmann <aherrmann@...e.com>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>,
Viresh Kumar <viresh.kumar@...aro.org>
Cc: linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
Stratos Karafotis <stratosk@...aphore.gr>,
Thomas Renninger <trenn@...e.com>
Subject: [PATCH v3 2/2] cpufreq/pcc-cpufreq: Make use of map_load_to_freq op
Commit 6393d6a102 (cpufreq: ondemand: Eliminate the deadband effect)
introduced a performance regression for systems using pcc-cpufreq and
ondemand governor. This is measurable with different workloads. E.g.
wall-clock time for kernel compilation significantly increased.
The elimination of the deadband effect significantly increased the
number of frequency changes with pcc-cpufreq.
Provide a pcc-cpufreq specific function that reintroduces the mapping
of load to frequency which was used before commit 6393d6a102 and hence
re-introduces the deadband effect for this cpufreq driver.
Performance results (kernel compile with different number of jobs)
based on 4.8.0-rc7 (with and w/o my patches on top) from
an HP ProLiant DL580 Gen8 system using pcc-cpufreq:
- Intel(R) Xeon(R) CPU E7-4890 v2 @ 2.80GHz
- 60 CPUs, 128GB RAM
pcc specific
generic_map_load_to_freq function map_load_to_freq function
# of jobs user sys elapsed % CPU user sys elapsed % CPU
2 445.56 111.22 273.35 203.00 413.19 102.34 250.97 205.00
4 445.61 126.10 143.12 399.00 390.56 120.79 127.25 401.20
8 483.51 150.84 82.17 771.40 354.22 140.09 64.20 769.60
16 628.01 185.54 55.02 1477.80 384.20 148.69 37.07 1436.60
32 818.58 205.51 37.02 2765.40 496.70 152.77 25.15 2581.40
64 406.22 51.84 13.84 3308.80 399.48 49.13 12.80 3505.80
120 413.61 49.06 14.54 3181.00 406.52 46.89 13.60 3331.60
Link: https://marc.info/?i=20160819121814.GA17296%40suselix.suse.de
Signed-off-by: Andreas Herrmann <aherrmann@...e.com>
---
drivers/cpufreq/Kconfig.x86 | 2 +-
drivers/cpufreq/pcc-cpufreq.c | 11 +++++++++++
2 files changed, 12 insertions(+), 1 deletion(-)
Kbuild test robot detected a build issue with my patch:
drivers/built-in.o: In function `pcc_cpufreq_cpu_exit':
>> pcc-cpufreq.c:(.text+0x321019): undefined reference to `od_unregister_map_load_to_freq_handler'
drivers/built-in.o: In function `pcc_cpufreq_cpu_init':
>> pcc-cpufreq.c:(.text+0x32136a): undefined reference to `od_register_map_load_to_freq_handler'
for configs that selected X86_PCC_CPUFREQ but not
CPU_FREQ_GOV_ONDEMAND.
This new patch version adds the required build dependency as my change
makes pcc-cpufreq dependent on cpufreq_ondemand.
Sorry for the omission in the previous patch version.
Regards,
Andreas
diff --git a/drivers/cpufreq/Kconfig.x86 b/drivers/cpufreq/Kconfig.x86
index adbd1de..f159726 100644
--- a/drivers/cpufreq/Kconfig.x86
+++ b/drivers/cpufreq/Kconfig.x86
@@ -18,7 +18,7 @@ config X86_INTEL_PSTATE
config X86_PCC_CPUFREQ
tristate "Processor Clocking Control interface driver"
- depends on ACPI && ACPI_PROCESSOR
+ depends on CPU_FREQ_GOV_ONDEMAND && ACPI && ACPI_PROCESSOR
help
This driver adds support for the PCC interface.
diff --git a/drivers/cpufreq/pcc-cpufreq.c b/drivers/cpufreq/pcc-cpufreq.c
index 3f0ce2a..1522747 100644
--- a/drivers/cpufreq/pcc-cpufreq.c
+++ b/drivers/cpufreq/pcc-cpufreq.c
@@ -39,6 +39,8 @@
#include <acpi/processor.h>
+#include "cpufreq_governor.h"
+
#define PCC_VERSION "1.10.00"
#define POLL_LOOPS 300
@@ -534,6 +536,12 @@ out_free:
return ret;
}
+static unsigned int pcc_map_load_to_freq(struct cpufreq_policy *policy,
+ unsigned int load)
+{
+ return (load * policy->cpuinfo.max_freq / 100);
+}
+
static int pcc_cpufreq_cpu_init(struct cpufreq_policy *policy)
{
unsigned int cpu = policy->cpu;
@@ -555,6 +563,8 @@ static int pcc_cpufreq_cpu_init(struct cpufreq_policy *policy)
policy->min = policy->cpuinfo.min_freq =
ioread32(&pcch_hdr->minimum_frequency) * 1000;
+ od_register_map_load_to_freq_handler(pcc_map_load_to_freq);
+
pr_debug("init: policy->max is %d, policy->min is %d\n",
policy->max, policy->min);
out:
@@ -563,6 +573,7 @@ out:
static int pcc_cpufreq_cpu_exit(struct cpufreq_policy *policy)
{
+ od_unregister_map_load_to_freq_handler();
return 0;
}
--
1.9.1
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