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authorLinus Torvalds <torvalds@linux-foundation.org>2014-06-04 07:48:54 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-06-04 07:48:54 -0700
commitc717d1561493c58d030405c7e30e35459db31912 (patch)
tree85c3a9521691b437cb7a76b701331d3992361f46
parent9e9a928eed8796a0a1aaed7e0b676db86ba84594 (diff)
parentbf8102228a8bf053051f311e5486042fe0542894 (diff)
Merge tag 'pm-3.15-final' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull intel pstate fixes from Rafael Wysocki: "Final power management fixes for 3.15 - Taking non-idle time into account when calculating core busy time was a mistake and led to a performance regression. Since the problem it was supposed to address is now taken care of in a different way, we don't need to do it any more, so drop the non-idle time tracking from intel_pstate. Dirk Brandewie. - Changing to fixed point math throughout the busy calculation introduced rounding errors that adversely affect the accuracy of intel_pstate's computations. Fix from Dirk Brandewie. - The PID controller algorithm used by intel_pstate assumes that the time interval between two adjacent samples will always be the same which is not the case for deferable timers (used by intel_pstate) when the system is idle. This leads to inaccurate predictions and artificially increases convergence times for the minimum P-state. Fix from Dirk Brandewie. - intel_pstate carries out computations using 32-bit variables that may overflow for large enough values of APERF/MPERF. Switch to using 64-bit variables for computations, from Doug Smythies" * tag 'pm-3.15-final' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm: intel_pstate: Improve initial busy calculation intel_pstate: add sample time scaling intel_pstate: Correct rounding in busy calculation intel_pstate: Remove C0 tracking
-rw-r--r--drivers/cpufreq/intel_pstate.c52
1 files changed, 31 insertions, 21 deletions
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c
index eab8ccfe6be..db2e45b4808 100644
--- a/drivers/cpufreq/intel_pstate.c
+++ b/drivers/cpufreq/intel_pstate.c
@@ -40,10 +40,10 @@
#define BYT_TURBO_VIDS 0x66d
-#define FRAC_BITS 6
+#define FRAC_BITS 8
#define int_tofp(X) ((int64_t)(X) << FRAC_BITS)
#define fp_toint(X) ((X) >> FRAC_BITS)
-#define FP_ROUNDUP(X) ((X) += 1 << FRAC_BITS)
+
static inline int32_t mul_fp(int32_t x, int32_t y)
{
@@ -59,8 +59,8 @@ struct sample {
int32_t core_pct_busy;
u64 aperf;
u64 mperf;
- unsigned long long tsc;
int freq;
+ ktime_t time;
};
struct pstate_data {
@@ -98,9 +98,9 @@ struct cpudata {
struct vid_data vid;
struct _pid pid;
+ ktime_t last_sample_time;
u64 prev_aperf;
u64 prev_mperf;
- unsigned long long prev_tsc;
struct sample sample;
};
@@ -200,7 +200,10 @@ static signed int pid_calc(struct _pid *pid, int32_t busy)
pid->last_err = fp_error;
result = pterm + mul_fp(pid->integral, pid->i_gain) + dterm;
-
+ if (result >= 0)
+ result = result + (1 << (FRAC_BITS-1));
+ else
+ result = result - (1 << (FRAC_BITS-1));
return (signed int)fp_toint(result);
}
@@ -560,47 +563,42 @@ static void intel_pstate_get_cpu_pstates(struct cpudata *cpu)
static inline void intel_pstate_calc_busy(struct cpudata *cpu,
struct sample *sample)
{
- int32_t core_pct;
- int32_t c0_pct;
+ int64_t core_pct;
+ int32_t rem;
- core_pct = div_fp(int_tofp((sample->aperf)),
- int_tofp((sample->mperf)));
- core_pct = mul_fp(core_pct, int_tofp(100));
- FP_ROUNDUP(core_pct);
+ core_pct = int_tofp(sample->aperf) * int_tofp(100);
+ core_pct = div_u64_rem(core_pct, int_tofp(sample->mperf), &rem);
- c0_pct = div_fp(int_tofp(sample->mperf), int_tofp(sample->tsc));
+ if ((rem << 1) >= int_tofp(sample->mperf))
+ core_pct += 1;
sample->freq = fp_toint(
mul_fp(int_tofp(cpu->pstate.max_pstate * 1000), core_pct));
- sample->core_pct_busy = mul_fp(core_pct, c0_pct);
+ sample->core_pct_busy = (int32_t)core_pct;
}
static inline void intel_pstate_sample(struct cpudata *cpu)
{
u64 aperf, mperf;
- unsigned long long tsc;
rdmsrl(MSR_IA32_APERF, aperf);
rdmsrl(MSR_IA32_MPERF, mperf);
- tsc = native_read_tsc();
aperf = aperf >> FRAC_BITS;
mperf = mperf >> FRAC_BITS;
- tsc = tsc >> FRAC_BITS;
+ cpu->last_sample_time = cpu->sample.time;
+ cpu->sample.time = ktime_get();
cpu->sample.aperf = aperf;
cpu->sample.mperf = mperf;
- cpu->sample.tsc = tsc;
cpu->sample.aperf -= cpu->prev_aperf;
cpu->sample.mperf -= cpu->prev_mperf;
- cpu->sample.tsc -= cpu->prev_tsc;
intel_pstate_calc_busy(cpu, &cpu->sample);
cpu->prev_aperf = aperf;
cpu->prev_mperf = mperf;
- cpu->prev_tsc = tsc;
}
static inline void intel_pstate_set_sample_time(struct cpudata *cpu)
@@ -614,13 +612,25 @@ static inline void intel_pstate_set_sample_time(struct cpudata *cpu)
static inline int32_t intel_pstate_get_scaled_busy(struct cpudata *cpu)
{
- int32_t core_busy, max_pstate, current_pstate;
+ int32_t core_busy, max_pstate, current_pstate, sample_ratio;
+ u32 duration_us;
+ u32 sample_time;
core_busy = cpu->sample.core_pct_busy;
max_pstate = int_tofp(cpu->pstate.max_pstate);
current_pstate = int_tofp(cpu->pstate.current_pstate);
core_busy = mul_fp(core_busy, div_fp(max_pstate, current_pstate));
- return FP_ROUNDUP(core_busy);
+
+ sample_time = (pid_params.sample_rate_ms * USEC_PER_MSEC);
+ duration_us = (u32) ktime_us_delta(cpu->sample.time,
+ cpu->last_sample_time);
+ if (duration_us > sample_time * 3) {
+ sample_ratio = div_fp(int_tofp(sample_time),
+ int_tofp(duration_us));
+ core_busy = mul_fp(core_busy, sample_ratio);
+ }
+
+ return core_busy;
}
static inline void intel_pstate_adjust_busy_pstate(struct cpudata *cpu)