src/patches/suse-2.6.27.39/patches.fixes/cpufreq_export_latency.patch

   1 From: Thomas Renninger <trenn@suse.de>
   2 Subject: CPUFREQ: Introduce /sys/devices/system/cpu/cpu*/cpufreq/cpuinfo_transition_latency
   3 References: bnc#464461
   4 Patch-Mainline: not yet
   5
   6 It's not only useful for the ondemand and conservative governors, but
   7 also for userspace daemons to know about the HW transition latency of
   8 the CPU.
   9 It is especially useful for userspace to know about this value when
  10 the ondemand or conservative governors are run. The sampling rate
  11 control value depends on it and for userspace being able to set sane
  12 tuning values there it has to know about the transition latency.
  13
  14 Signed-off-by: Thomas Renninger <trenn@suse.de>
  15
  16 ---
  17  Documentation/cpu-freq/user-guide.txt |   12 ++++++++++++
  18  drivers/cpufreq/cpufreq.c             |    3 +++
  19  2 files changed, 15 insertions(+)
  20
  21 Index: linux-2.6.27/Documentation/cpu-freq/user-guide.txt
  22 ===================================================================
  23 --- linux-2.6.27.orig/Documentation/cpu-freq/user-guide.txt
  24 +++ linux-2.6.27/Documentation/cpu-freq/user-guide.txt
  25 @@ -142,6 +142,18 @@ cpuinfo_min_freq :         this file shows the
  26                                 frequency the processor can run at(in kHz)
  27  cpuinfo_max_freq :             this file shows the maximum operating
  28                                 frequency the processor can run at(in kHz)
  29 +cpuinfo_transition_latency     The time it takes on this CPU to
  30 +                               switch between two frequencies in nano
  31 +                               seconds. If unknown or known to be
  32 +                               that high that the driver does not
  33 +                               work with the ondemand governor, -1
  34 +                               (CPUFREQ_ETERNAL) will be returned.
  35 +                               Using this information can be useful
  36 +                               to choose an appropriate polling
  37 +                               frequency for a kernel governor or
  38 +                               userspace daemon. Make sure to not
  39 +                               switch the frequency too often
  40 +                               resulting in performance loss.
  41  scaling_driver :               this file shows what cpufreq driver is
  42                                 used to set the frequency on this CPU
  43
  44 Index: linux-2.6.27/drivers/cpufreq/cpufreq.c
  45 ===================================================================
  46 --- linux-2.6.27.orig/drivers/cpufreq/cpufreq.c
  47 +++ linux-2.6.27/drivers/cpufreq/cpufreq.c
  48 @@ -455,6 +455,7 @@ static ssize_t show_##file_name                             \
  49
  50  show_one(cpuinfo_min_freq, cpuinfo.min_freq);
  51  show_one(cpuinfo_max_freq, cpuinfo.max_freq);
  52 +show_one(cpuinfo_transition_latency, cpuinfo.transition_latency);
  53  show_one(scaling_min_freq, min);
  54  show_one(scaling_max_freq, max);
  55  show_one(scaling_cur_freq, cur);
  56 @@ -660,6 +661,7 @@ __ATTR(_name, 0644, show_##_name, store_
  57  define_one_ro0400(cpuinfo_cur_freq);
  58  define_one_ro(cpuinfo_min_freq);
  59  define_one_ro(cpuinfo_max_freq);
  60 +define_one_ro(cpuinfo_transition_latency);
  61  define_one_ro(scaling_available_governors);
  62  define_one_ro(scaling_driver);
  63  define_one_ro(scaling_cur_freq);
  64 @@ -673,6 +675,7 @@ define_one_rw(scaling_setspeed);
  65  static struct attribute *default_attrs[] = {
  66         &cpuinfo_min_freq.attr,
  67         &cpuinfo_max_freq.attr,
  68 +       &cpuinfo_transition_latency.attr,
  69         &scaling_min_freq.attr,
  70         &scaling_max_freq.attr,
  71         &affected_cpus.attr,