66 lines
2.4 KiB
Diff
66 lines
2.4 KiB
Diff
From: Thomas Renninger <trenn@suse.de>
|
|
Subject: CPUFREQ: ondemand: Limit default sampling rate to 300ms max.
|
|
References: bnc#464461
|
|
Patch-Mainline: never, SLE11 only
|
|
|
|
Modified for SP1 by Jiri Bohac <jbohac@suse.cz>
|
|
|
|
HW cpufreq drivers (e.g. all non-acpi AMD) may report too high latency values.
|
|
The default sampling rate (how often the ondemand/conservative governor
|
|
checks for frequency adjustments) may therefore be much too high,
|
|
resulting in performance loss.
|
|
|
|
Restrict default sampling rate to 300ms. 333ms sampling rate is field
|
|
tested with userspace governors, 300ms should be a fine maximum default
|
|
value for the ondemand kernel governor for all HW out there.
|
|
|
|
Set default up_threshold to 40 on multi core systems.
|
|
This should avoid effects where two CPU intensive threads are waiting on
|
|
each other on separate cores. On a single core machine these would all be
|
|
processed on one core resulting in higher utilization of the one core.
|
|
|
|
---
|
|
drivers/cpufreq/cpufreq_ondemand.c | 24 ++++++++++++++++++++++++
|
|
1 file changed, 24 insertions(+)
|
|
|
|
--- a/drivers/cpufreq/cpufreq_ondemand.c
|
|
+++ b/drivers/cpufreq/cpufreq_ondemand.c
|
|
@@ -35,6 +35,7 @@
|
|
#define MICRO_FREQUENCY_MIN_SAMPLE_RATE (10000)
|
|
#define MIN_FREQUENCY_UP_THRESHOLD (11)
|
|
#define MAX_FREQUENCY_UP_THRESHOLD (100)
|
|
+#define MAX_DEFAULT_SAMPLING_RATE (300 * 1000U)
|
|
|
|
/*
|
|
* The polling frequency of this governor depends on the capability of
|
|
@@ -679,6 +680,29 @@ static int cpufreq_governor_dbs(struct c
|
|
dbs_tuners_ins.sampling_rate =
|
|
max(min_sampling_rate,
|
|
latency * LATENCY_MULTIPLIER);
|
|
+ /*
|
|
+ * Cut def_sampling rate to 300ms if it was above,
|
|
+ * still consider to not set it above latency
|
|
+ * transition * 100
|
|
+ */
|
|
+ if (dbs_tuners_ins.sampling_rate > MAX_DEFAULT_SAMPLING_RATE) {
|
|
+ dbs_tuners_ins.sampling_rate =
|
|
+ max(min_sampling_rate, MAX_DEFAULT_SAMPLING_RATE);
|
|
+ printk(KERN_INFO "CPUFREQ: ondemand sampling "
|
|
+ "rate set to %d ms\n",
|
|
+ dbs_tuners_ins.sampling_rate / 1000);
|
|
+ }
|
|
+ /*
|
|
+ * Be conservative in respect to performance.
|
|
+ * If an application calculates using two threads
|
|
+ * depending on each other, they will be run on several
|
|
+ * CPU cores resulting on 50% load on both.
|
|
+ * SLED might still want to prefer 80% up_threshold
|
|
+ * by default, but we cannot differ that here.
|
|
+ */
|
|
+ if (num_online_cpus() > 1)
|
|
+ dbs_tuners_ins.up_threshold =
|
|
+ DEF_FREQUENCY_UP_THRESHOLD / 2;
|
|
}
|
|
mutex_unlock(&dbs_mutex);
|
|
|