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cpufreq: interactive: default go_hispeed_load 99%, doc updates

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Update default go_hispeed_load from 85% to 99%.  Recent changes to the
governor now use a default target_load of 90%.  go_hispeed_load should
not be lower than the target load for hispeed_freq, which could lead
to oscillating speed decisions.  Other recent changes reduce the need
to dampen speed jumps on load spikes, while input event boosts from
userspace are the preferred method for anticipating load spikes with
UI impacts.

General update to the documentation to reflect recent changes.

Change-Id: I1b92f3091f42c04b10503cd1169a943b5dfd6faf
Signed-off-by: Todd Poynor <toddpoynor@google.com>
This commit is contained in:
Todd Poynor 2012-12-21 15:13:01 -08:00 • committed by John Stultz
parent 1dc7486fd8
commit b4f2820d79
2 changed files with 32 additions and 32 deletions
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62
Documentation/cpu-freq/governors.txt
View file

@ -224,23 +224,8 @@ sampling rate.
The CPUfreq governor "interactive" is designed for latency-sensitive,
interactive workloads. This governor sets the CPU speed depending on
usage, similar to "ondemand" and "conservative" governors. However,
the governor is more aggressive about scaling the CPU speed up in
response to CPU-intensive activity.
Sampling the CPU load every X ms can lead to under-powering the CPU
for X ms, leading to dropped frames, stuttering UI, etc. Instead of
sampling the cpu at a specified rate, the interactive governor will
check whether to scale the cpu frequency up soon after coming out of
idle. When the cpu comes out of idle, a timer is configured to fire
within 1-2 ticks. If the cpu is very busy between exiting idle and
when the timer fires then we assume the cpu is underpowered and ramp
to MAX speed.
If the cpu was not sufficiently busy to immediately ramp to MAX speed,
then governor evaluates the cpu load since the last speed adjustment,
choosing the highest value between that longer-term load or the
short-term load since idle exit to determine the cpu speed to ramp to.
usage, similar to "ondemand" and "conservative" governors, but with a
different set of configurable behaviors.
The tuneable values for this governor are:
@ -262,36 +247,51 @@ values also usually appear in an ascending order. The default is
target load 90% for all speeds.
min_sample_time: The minimum amount of time to spend at the current
frequency before ramping down. This is to ensure that the governor has
seen enough historic cpu load data to determine the appropriate
workload. Default is 80000 uS.
frequency before ramping down. Default is 80000 uS.
hispeed_freq: An intermediate "hi speed" at which to initially ramp
when CPU load hits the value specified in go_hispeed_load. If load
stays high for the amount of time specified in above_hispeed_delay,
then speed may be bumped higher. Default is maximum speed.
then speed may be bumped higher. Default is the maximum speed
allowed by the policy at governor initialization time.
go_hispeed_load: The CPU load at which to ramp to the intermediate "hi
speed". Default is 85%.
go_hispeed_load: The CPU load at which to ramp to hispeed_freq.
Default is 99%.
above_hispeed_delay: Once speed is set to hispeed_freq, wait for this
long before bumping speed higher in response to continued high load.
above_hispeed_delay: When speed is at or above hispeed_freq, wait for
this long before raising speed in response to continued high load.
Default is 20000 uS.
timer_rate: Sample rate for reevaluating cpu load when the system is
not idle. Default is 20000 uS.
timer_rate: Sample rate for reevaluating CPU load when the CPU is not
idle. A deferrable timer is used, such that the CPU will not be woken
from idle to service this timer until something else needs to run.
(The maximum time to allow deferring this timer when not running at
minimum speed is configurable via timer_slack.) Default is 20000 uS.
input_boost: If non-zero, boost speed of all CPUs to hispeed_freq on
touchscreen activity. Default is 0.
timer_slack: Maximum additional time to defer handling the governor
sampling timer beyond timer_rate when running at speeds above the
minimum. For platforms that consume additional power at idle when
CPUs are running at speeds greater than minimum, this places an upper
bound on how long the timer will be deferred prior to re-evaluating
load and dropping speed. For example, if timer_rate is 20000uS and
timer_slack is 10000uS then timers will be deferred for up to 30msec
when not at lowest speed. A value of -1 means defer timers
indefinitely at all speeds. Default is 80000 uS.
boost: If non-zero, immediately boost speed of all CPUs to at least
hispeed_freq until zero is written to this attribute. If zero, allow
CPU speeds to drop below hispeed_freq according to load as usual.
Default is zero.
boostpulse: Immediately boost speed of all CPUs to hispeed_freq for
min_sample_time, after which speeds are allowed to drop below
boostpulse: On each write, immediately boost speed of all CPUs to
hispeed_freq for at least the period of time specified by
boostpulse_duration, after which speeds are allowed to drop below
hispeed_freq according to load as usual.
boostpulse_duration: Length of time to hold CPU speed at hispeed_freq
on a write to boostpulse, before allowing speed to drop according to
load as usual. Default is 80000 uS.
3. The Governor Interface in the CPUfreq Core
=============================================

2
drivers/cpufreq/cpufreq_interactive.c
View file

@ -66,7 +66,7 @@ static spinlock_t speedchange_cpumask_lock;
static unsigned int hispeed_freq;
/* Go to hi speed when CPU load at or above this value. */
#define DEFAULT_GO_HISPEED_LOAD 85
#define DEFAULT_GO_HISPEED_LOAD 99
static unsigned long go_hispeed_load;
/* Target load. Lower values result in higher CPU speeds. */