lkml.org 
[lkml]   [2010]   [May]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 8/7] cpufreq: make the iowait-is-busy-time a sysfs tunable
    On Mon 2010-05-03 20:48:18, Arjan van de Ven wrote:
    > On Tue, 27 Apr 2010 13:39:34 +0200
    > Thomas Renninger <trenn@suse.de> wrote:
    >
    > > On Friday 23 April 2010 06:08:19 pm Arjan van de Ven wrote:
    > > > On Fri, 23 Apr 2010 10:50:10 +0200
    > > > Thomas Renninger <trenn@suse.de> wrote:
    > > > Especially on battery, users will appreciate some minutes
    > > >
    > > > > of more battery lifetime and do not care about some ms of IO
    > > > > latencies.
    > > >
    > > > the assumption that power doesn't matter on AC is a huge fiction
    > > > that any data center operator would love to get out of everyones
    > > > head as quickly as possible.
    > >
    > > Have I said power doesn't matter on AC?
    > > Do you agree that a datacenter has different performance vs power
    > > tradeoff demands as a battery driven mobile device?
    > >
    > > Back to the topic:
    > > As you did not answer on my (several) sysfs knob request(s), I expect
    > > you agree with it and will add one.
    > >
    >
    > yup it makes sense to have a sysfs knob with a sane default value
    >
    > From: Arjan van de Ven <arjan@linux.intel.com>
    > Subject: [PATCH] cpufreq: make the iowait-is-busy-time a sysfs tunable
    >
    > Pavel Machek pointed out that not all CPUs have an efficient idle
    > at high frequency. Specifically, older Intel and various AMD cpus
    > would get a higher power usage when copying files from USB.
    >
    > Mike Chan pointed out that the same is true for various ARM chips
    > as well.
    >
    > Thomas Renninger suggested to make this a sysfs tunable with a
    > reasonable default.
    >
    > This patch adds a sysfs tunable for the new behavior, and uses
    > a very simple function to determine a reasonable default, depending
    > on the CPU vendor/type.
    >
    > Signed-off-by: Arjan van de Ven <arjan@linux.intel.com>

    ACK.

    > ---
    > drivers/cpufreq/cpufreq_ondemand.c | 46 +++++++++++++++++++++++++++++++++++-
    > 1 files changed, 45 insertions(+), 1 deletions(-)
    >
    > diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
    > index ed472f8..4877e8f 100644
    > --- a/drivers/cpufreq/cpufreq_ondemand.c
    > +++ b/drivers/cpufreq/cpufreq_ondemand.c
    > @@ -109,6 +109,7 @@ static struct dbs_tuners {
    > unsigned int down_differential;
    > unsigned int ignore_nice;
    > unsigned int powersave_bias;
    > + unsigned int io_is_busy;
    > } dbs_tuners_ins = {
    > .up_threshold = DEF_FREQUENCY_UP_THRESHOLD,
    > .down_differential = DEF_FREQUENCY_DOWN_DIFFERENTIAL,
    > @@ -260,6 +261,7 @@ static ssize_t show_##file_name \
    > return sprintf(buf, "%u\n", dbs_tuners_ins.object); \
    > }
    > show_one(sampling_rate, sampling_rate);
    > +show_one(io_is_busy, io_is_busy);
    > show_one(up_threshold, up_threshold);
    > show_one(ignore_nice_load, ignore_nice);
    > show_one(powersave_bias, powersave_bias);
    > @@ -310,6 +312,22 @@ static ssize_t store_sampling_rate(struct kobject *a, struct attribute *b,
    > return count;
    > }
    >
    > +static ssize_t store_io_is_busy(struct kobject *a, struct attribute *b,
    > + const char *buf, size_t count)
    > +{
    > + unsigned int input;
    > + int ret;
    > + ret = sscanf(buf, "%u", &input);
    > + if (ret != 1)
    > + return -EINVAL;
    > +
    > + mutex_lock(&dbs_mutex);
    > + dbs_tuners_ins.io_is_busy = !!input;
    > + mutex_unlock(&dbs_mutex);
    > +
    > + return count;
    > +}
    > +
    > static ssize_t store_up_threshold(struct kobject *a, struct attribute *b,
    > const char *buf, size_t count)
    > {
    > @@ -392,6 +410,7 @@ static struct global_attr _name = \
    > __ATTR(_name, 0644, show_##_name, store_##_name)
    >
    > define_one_rw(sampling_rate);
    > +define_one_rw(io_is_busy);
    > define_one_rw(up_threshold);
    > define_one_rw(ignore_nice_load);
    > define_one_rw(powersave_bias);
    > @@ -403,6 +422,7 @@ static struct attribute *dbs_attributes[] = {
    > &up_threshold.attr,
    > &ignore_nice_load.attr,
    > &powersave_bias.attr,
    > + &io_is_busy.attr,
    > NULL
    > };
    >
    > @@ -527,7 +547,7 @@ static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
    > * from the cpu idle time.
    > */
    >
    > - if (idle_time >= iowait_time)
    > + if (dbs_tuners_ins.io_is_busy && idle_time >= iowait_time)
    > idle_time -= iowait_time;
    >
    > if (unlikely(!wall_time || wall_time < idle_time))
    > @@ -643,6 +663,29 @@ static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
    > cancel_delayed_work_sync(&dbs_info->work);
    > }
    >
    > +/*
    > + * Not all CPUs want IO time to be accounted as busy; this depends on how
    > + * efficient idling at a higher frequency/voltage is.
    > + * Pavel Machek says this is not so for various generations of AMD and old
    > + * Intel systems.
    > + * Mike Chan (android.com) says this is also not true for ARM.
    > + * Because of this, whitelist specific known (series) of CPUs by default, and
    > + * leave all others up to the user.
    > + */
    > +static int should_io_be_busy(void)
    > +{
    > +#if defined(CONFIG_X86)
    > + /*
    > + * For Intel, Core 2 (model 15) and later have an efficient idle.
    > + */
    > + if (boot_cpu_data.x86_vendor == X86_VENDOR_INTEL &&
    > + boot_cpu_data.x86 == 6 &&
    > + boot_cpu_data.x86_model >= 15)
    > + return 1;
    > +#endif
    > + return 0;
    > +}
    > +
    > static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
    > unsigned int event)
    > {
    > @@ -705,6 +748,7 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
    > dbs_tuners_ins.sampling_rate =
    > max(min_sampling_rate,
    > latency * LATENCY_MULTIPLIER);
    > + dbs_tuners_ins.io_is_busy = should_io_be_busy();
    > }
    > mutex_unlock(&dbs_mutex);
    >

    --
    (english) http://www.livejournal.com/~pavelmachek
    (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


    \
     
     \ /
      Last update: 2010-05-04 07:47    [W:0.035 / U:100.876 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site