Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753740AbaBYSfx (ORCPT ); Tue, 25 Feb 2014 13:35:53 -0500 Received: from mail-pd0-f173.google.com ([209.85.192.173]:53690 "EHLO mail-pd0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753710AbaBYSfv (ORCPT ); Tue, 25 Feb 2014 13:35:51 -0500 From: dirk.brandewie@gmail.com To: linux-pm@vger.kernel.org Cc: linux-kernel@vger.kernel.org, gregkh@linuxfoundation.org, rafael.j.wysocki@intel.com, gf435@gmx.net, bp@alien8.de, dirk.brandewie@gmail.com, Dirk Brandewie Subject: [PATCH] intel_pstate: Change busy calculation to use fixed point math. Date: Tue, 25 Feb 2014 10:35:37 -0800 Message-Id: <1393353337-19778-1-git-send-email-dirk.j.brandewie@intel.com> X-Mailer: git-send-email 1.8.3.1 In-Reply-To: <20140219224752.GA370@kroah.com> References: <20140219224752.GA370@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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 --- 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) -- 1.8.3.1 -- 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/