Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753656AbaBZAY2 (ORCPT ); Tue, 25 Feb 2014 19:24:28 -0500 Received: from v094114.home.net.pl ([79.96.170.134]:64943 "HELO v094114.home.net.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1752813AbaBZAY1 (ORCPT ); Tue, 25 Feb 2014 19:24:27 -0500 From: "Rafael J. Wysocki" To: dirk.brandewie@gmail.com Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, rafael.j.wysocki@intel.com, gf435@gmx.net, bp@alien8.de, Dirk Brandewie Subject: Re: [PATCH] intel_pstate: Change busy calculation to use fixed point math. Date: Wed, 26 Feb 2014 01:39:25 +0100 Message-ID: <1509075.br8MLUFIAK@vostro.rjw.lan> User-Agent: KMail/4.11.5 (Linux/3.13.0+; KDE/4.11.5; x86_64; ; ) In-Reply-To: <1393353337-19778-1-git-send-email-dirk.j.brandewie@intel.com> References: <20140219224752.GA370@kroah.com> <1393353337-19778-1-git-send-email-dirk.j.brandewie@intel.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="utf-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tuesday, February 25, 2014 10:35:37 AM dirk.brandewie@gmail.com wrote: > From: Dirk Brandewie > > Commit fcb6a15c2e Take core C0 time into account for core busy calculation. > > Introduced a regression on some processor SKUs supported by > intel_pstate. This was caused by 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% 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 > > References: > https://lkml.org/lkml/2014/2/19/626 > https://bugzilla.kernel.org/show_bug.cgi?id=70941 > > Signed-off-by: Dirk Brandewie Queued up as a fix for 3.14. Thanks! > --- > drivers/cpufreq/intel_pstate.c | 28 ++++++++++++++++++---------- > 1 file changed, 18 insertions(+), 10 deletions(-) > > diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c > index e908161..2cd36b9 100644 > --- a/drivers/cpufreq/intel_pstate.c > +++ b/drivers/cpufreq/intel_pstate.c > @@ -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) > -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/