intel_pstate: Change busy calculation to use fixed point math.
Commitfcb6a15c2e
(intel_pstate: Take core C0 time into account for core busy calculation) introduced a regression on some processor SKUs supported by intel_pstate. This was due to the truncation caused by using integer math to calculate core busy and C0 percentages. On a i7-4770K processor operating at 800Mhz going to 100% utilization the percent busy of the CPU using integer math is 22%, but it actually is 22.85%. This value scaled to the current frequency returned 97 which the PID interpreted as no error and did not adjust the P state. Tested on i7-4770K, i7-2600, i5-3230M. Fixes:fcb6a15c2e
(intel_pstate: Take core C0 time into account for core busy calculation) References: https://lkml.org/lkml/2014/2/19/626 References: https://bugzilla.kernel.org/show_bug.cgi?id=70941 Signed-off-by: Dirk Brandewie <dirk.j.brandewie@intel.com> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
This commit is contained in:
parent
cfbf8d4857
commit
e66c176837
|
@ -39,9 +39,10 @@
|
|||
#define BYT_TURBO_RATIOS 0x66c
|
||||
|
||||
|
||||
#define FRAC_BITS 8
|
||||
#define FRAC_BITS 6
|
||||
#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)
|
||||
{
|
||||
|
@ -556,18 +557,20 @@ static void intel_pstate_get_cpu_pstates(struct cpudata *cpu)
|
|||
static inline void intel_pstate_calc_busy(struct cpudata *cpu,
|
||||
struct sample *sample)
|
||||
{
|
||||
u64 core_pct;
|
||||
u64 c0_pct;
|
||||
int32_t core_pct;
|
||||
int32_t c0_pct;
|
||||
|
||||
core_pct = div64_u64(sample->aperf * 100, sample->mperf);
|
||||
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);
|
||||
|
||||
c0_pct = div_fp(int_tofp(sample->mperf), int_tofp(sample->tsc));
|
||||
|
||||
c0_pct = div64_u64(sample->mperf * 100, sample->tsc);
|
||||
sample->freq = fp_toint(
|
||||
mul_fp(int_tofp(cpu->pstate.max_pstate),
|
||||
int_tofp(core_pct * 1000)));
|
||||
mul_fp(int_tofp(cpu->pstate.max_pstate * 1000), core_pct));
|
||||
|
||||
sample->core_pct_busy = mul_fp(int_tofp(core_pct),
|
||||
div_fp(int_tofp(c0_pct + 1), int_tofp(100)));
|
||||
sample->core_pct_busy = mul_fp(core_pct, c0_pct);
|
||||
}
|
||||
|
||||
static inline void intel_pstate_sample(struct cpudata *cpu)
|
||||
|
@ -579,6 +582,10 @@ static inline void intel_pstate_sample(struct cpudata *cpu)
|
|||
rdmsrl(MSR_IA32_MPERF, mperf);
|
||||
tsc = native_read_tsc();
|
||||
|
||||
aperf = aperf >> FRAC_BITS;
|
||||
mperf = mperf >> FRAC_BITS;
|
||||
tsc = tsc >> FRAC_BITS;
|
||||
|
||||
cpu->sample_ptr = (cpu->sample_ptr + 1) % SAMPLE_COUNT;
|
||||
cpu->samples[cpu->sample_ptr].aperf = aperf;
|
||||
cpu->samples[cpu->sample_ptr].mperf = mperf;
|
||||
|
@ -610,7 +617,8 @@ static inline int32_t intel_pstate_get_scaled_busy(struct cpudata *cpu)
|
|||
core_busy = cpu->samples[cpu->sample_ptr].core_pct_busy;
|
||||
max_pstate = int_tofp(cpu->pstate.max_pstate);
|
||||
current_pstate = int_tofp(cpu->pstate.current_pstate);
|
||||
return mul_fp(core_busy, div_fp(max_pstate, current_pstate));
|
||||
core_busy = mul_fp(core_busy, div_fp(max_pstate, current_pstate));
|
||||
return FP_ROUNDUP(core_busy);
|
||||
}
|
||||
|
||||
static inline void intel_pstate_adjust_busy_pstate(struct cpudata *cpu)
|
||||
|
|
Loading…
Reference in a new issue