* [PATCH] intel_pstate: Avoid pointless FRAC_BITS shifts under div_fp()
@ 2016-03-31 13:46 Rafael J. Wysocki
2016-04-01 7:44 ` Philippe Longepe
0 siblings, 1 reply; 3+ messages in thread
From: Rafael J. Wysocki @ 2016-03-31 13:46 UTC (permalink / raw)
To: Linux PM list, Srinivas Pandruvada; +Cc: Linux Kernel Mailing List
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
There are multiple places in intel_pstate where int_tofp() is applied
to both arguments of div_fp(), but this is pointless, because int_tofp()
simply shifts its argument to the left by FRAC_BITS which mathematically
is equivalent to multuplication by 2^FRAC_BITS, so if this is done
to both arguments of a division, the extra factors will cancel each
other during that operation anyway.
Drop the pointless int_tofp() applied to div_fp() arguments throughout
the driver.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/cpufreq/intel_pstate.c | 27 +++++++++++----------------
1 file changed, 11 insertions(+), 16 deletions(-)
Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -206,17 +206,17 @@ static inline void pid_reset(struct _pid
static inline void pid_p_gain_set(struct _pid *pid, int percent)
{
- pid->p_gain = div_fp(int_tofp(percent), int_tofp(100));
+ pid->p_gain = div_fp(percent, 100);
}
static inline void pid_i_gain_set(struct _pid *pid, int percent)
{
- pid->i_gain = div_fp(int_tofp(percent), int_tofp(100));
+ pid->i_gain = div_fp(percent, 100);
}
static inline void pid_d_gain_set(struct _pid *pid, int percent)
{
- pid->d_gain = div_fp(int_tofp(percent), int_tofp(100));
+ pid->d_gain = div_fp(percent, 100);
}
static signed int pid_calc(struct _pid *pid, int32_t busy)
@@ -394,7 +394,7 @@ static ssize_t show_turbo_pct(struct kob
total = cpu->pstate.turbo_pstate - cpu->pstate.min_pstate + 1;
no_turbo = cpu->pstate.max_pstate - cpu->pstate.min_pstate + 1;
- turbo_fp = div_fp(int_tofp(no_turbo), int_tofp(total));
+ turbo_fp = div_fp(no_turbo, total);
turbo_pct = 100 - fp_toint(mul_fp(turbo_fp, int_tofp(100)));
return sprintf(buf, "%u\n", turbo_pct);
}
@@ -465,8 +465,7 @@ static ssize_t store_max_perf_pct(struct
limits->max_perf_pct);
limits->max_perf_pct = max(limits->min_perf_pct,
limits->max_perf_pct);
- limits->max_perf = div_fp(int_tofp(limits->max_perf_pct),
- int_tofp(100));
+ limits->max_perf = div_fp(limits->max_perf_pct, 100);
if (hwp_active)
intel_pstate_hwp_set_online_cpus();
@@ -490,8 +489,7 @@ static ssize_t store_min_perf_pct(struct
limits->min_perf_pct);
limits->min_perf_pct = min(limits->max_perf_pct,
limits->min_perf_pct);
- limits->min_perf = div_fp(int_tofp(limits->min_perf_pct),
- int_tofp(100));
+ limits->min_perf = div_fp(limits->min_perf_pct, 100);
if (hwp_active)
intel_pstate_hwp_set_online_cpus();
@@ -973,8 +971,8 @@ static inline int32_t get_target_pstate_
* specified pstate.
*/
core_busy = cpu->sample.core_pct_busy;
- max_pstate = int_tofp(cpu->pstate.max_pstate_physical);
- current_pstate = int_tofp(cpu->pstate.current_pstate);
+ max_pstate = cpu->pstate.max_pstate_physical;
+ current_pstate = cpu->pstate.current_pstate;
core_busy = mul_fp(core_busy, div_fp(max_pstate, current_pstate));
/*
@@ -986,8 +984,7 @@ static inline int32_t get_target_pstate_
duration_ns = cpu->sample.time - cpu->last_sample_time;
if ((s64)duration_ns > pid_params.sample_rate_ns * 3
&& cpu->last_sample_time > 0) {
- sample_ratio = div_fp(int_tofp(pid_params.sample_rate_ns),
- int_tofp(duration_ns));
+ sample_ratio = div_fp(pid_params.sample_rate_ns, duration_ns);
core_busy = mul_fp(core_busy, sample_ratio);
}
@@ -1167,10 +1164,8 @@ static int intel_pstate_set_policy(struc
/* Make sure min_perf_pct <= max_perf_pct */
limits->min_perf_pct = min(limits->max_perf_pct, limits->min_perf_pct);
- limits->min_perf = div_fp(int_tofp(limits->min_perf_pct),
- int_tofp(100));
- limits->max_perf = div_fp(int_tofp(limits->max_perf_pct),
- int_tofp(100));
+ limits->min_perf = div_fp(limits->min_perf_pct, 100);
+ limits->max_perf = div_fp(limits->max_perf_pct, 100);
out:
intel_pstate_set_update_util_hook(policy->cpu);
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] intel_pstate: Avoid pointless FRAC_BITS shifts under div_fp()
2016-03-31 13:46 [PATCH] intel_pstate: Avoid pointless FRAC_BITS shifts under div_fp() Rafael J. Wysocki
@ 2016-04-01 7:44 ` Philippe Longepe
2016-04-04 1:31 ` Rafael J. Wysocki
0 siblings, 1 reply; 3+ messages in thread
From: Philippe Longepe @ 2016-04-01 7:44 UTC (permalink / raw)
To: Rafael J. Wysocki, Linux PM list, Srinivas Pandruvada
Cc: Linux Kernel Mailing List
I proposed also to simplify the intel_pstate_calc_busy function:
core_pct = int_tofp(sample->aperf) * int_tofp(100);
core_pct = div64_u64(core_pct, int_tofp(sample->mperf));
is equivalent to:
core_pct = sample->aperf * int_tofp(100);
core_pct = div64_u64(core_pct, sample->mperf);
Regards,
Philippe,
On 31/03/2016 15:46, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> There are multiple places in intel_pstate where int_tofp() is applied
> to both arguments of div_fp(), but this is pointless, because int_tofp()
> simply shifts its argument to the left by FRAC_BITS which mathematically
> is equivalent to multuplication by 2^FRAC_BITS, so if this is done
> to both arguments of a division, the extra factors will cancel each
> other during that operation anyway.
>
> Drop the pointless int_tofp() applied to div_fp() arguments throughout
> the driver.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> ---
> drivers/cpufreq/intel_pstate.c | 27 +++++++++++----------------
> 1 file changed, 11 insertions(+), 16 deletions(-)
>
> Index: linux-pm/drivers/cpufreq/intel_pstate.c
> ===================================================================
> --- linux-pm.orig/drivers/cpufreq/intel_pstate.c
> +++ linux-pm/drivers/cpufreq/intel_pstate.c
> @@ -206,17 +206,17 @@ static inline void pid_reset(struct _pid
>
> static inline void pid_p_gain_set(struct _pid *pid, int percent)
> {
> - pid->p_gain = div_fp(int_tofp(percent), int_tofp(100));
> + pid->p_gain = div_fp(percent, 100);
> }
>
> static inline void pid_i_gain_set(struct _pid *pid, int percent)
> {
> - pid->i_gain = div_fp(int_tofp(percent), int_tofp(100));
> + pid->i_gain = div_fp(percent, 100);
> }
>
> static inline void pid_d_gain_set(struct _pid *pid, int percent)
> {
> - pid->d_gain = div_fp(int_tofp(percent), int_tofp(100));
> + pid->d_gain = div_fp(percent, 100);
> }
>
> static signed int pid_calc(struct _pid *pid, int32_t busy)
> @@ -394,7 +394,7 @@ static ssize_t show_turbo_pct(struct kob
>
> total = cpu->pstate.turbo_pstate - cpu->pstate.min_pstate + 1;
> no_turbo = cpu->pstate.max_pstate - cpu->pstate.min_pstate + 1;
> - turbo_fp = div_fp(int_tofp(no_turbo), int_tofp(total));
> + turbo_fp = div_fp(no_turbo, total);
> turbo_pct = 100 - fp_toint(mul_fp(turbo_fp, int_tofp(100)));
> return sprintf(buf, "%u\n", turbo_pct);
> }
> @@ -465,8 +465,7 @@ static ssize_t store_max_perf_pct(struct
> limits->max_perf_pct);
> limits->max_perf_pct = max(limits->min_perf_pct,
> limits->max_perf_pct);
> - limits->max_perf = div_fp(int_tofp(limits->max_perf_pct),
> - int_tofp(100));
> + limits->max_perf = div_fp(limits->max_perf_pct, 100);
>
> if (hwp_active)
> intel_pstate_hwp_set_online_cpus();
> @@ -490,8 +489,7 @@ static ssize_t store_min_perf_pct(struct
> limits->min_perf_pct);
> limits->min_perf_pct = min(limits->max_perf_pct,
> limits->min_perf_pct);
> - limits->min_perf = div_fp(int_tofp(limits->min_perf_pct),
> - int_tofp(100));
> + limits->min_perf = div_fp(limits->min_perf_pct, 100);
>
> if (hwp_active)
> intel_pstate_hwp_set_online_cpus();
> @@ -973,8 +971,8 @@ static inline int32_t get_target_pstate_
> * specified pstate.
> */
> core_busy = cpu->sample.core_pct_busy;
> - max_pstate = int_tofp(cpu->pstate.max_pstate_physical);
> - current_pstate = int_tofp(cpu->pstate.current_pstate);
> + max_pstate = cpu->pstate.max_pstate_physical;
> + current_pstate = cpu->pstate.current_pstate;
> core_busy = mul_fp(core_busy, div_fp(max_pstate, current_pstate));
>
> /*
> @@ -986,8 +984,7 @@ static inline int32_t get_target_pstate_
> duration_ns = cpu->sample.time - cpu->last_sample_time;
> if ((s64)duration_ns > pid_params.sample_rate_ns * 3
> && cpu->last_sample_time > 0) {
> - sample_ratio = div_fp(int_tofp(pid_params.sample_rate_ns),
> - int_tofp(duration_ns));
> + sample_ratio = div_fp(pid_params.sample_rate_ns, duration_ns);
> core_busy = mul_fp(core_busy, sample_ratio);
> }
>
> @@ -1167,10 +1164,8 @@ static int intel_pstate_set_policy(struc
> /* Make sure min_perf_pct <= max_perf_pct */
> limits->min_perf_pct = min(limits->max_perf_pct, limits->min_perf_pct);
>
> - limits->min_perf = div_fp(int_tofp(limits->min_perf_pct),
> - int_tofp(100));
> - limits->max_perf = div_fp(int_tofp(limits->max_perf_pct),
> - int_tofp(100));
> + limits->min_perf = div_fp(limits->min_perf_pct, 100);
> + limits->max_perf = div_fp(limits->max_perf_pct, 100);
>
> out:
> intel_pstate_set_update_util_hook(policy->cpu);
>
> --
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> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] intel_pstate: Avoid pointless FRAC_BITS shifts under div_fp()
2016-04-01 7:44 ` Philippe Longepe
@ 2016-04-04 1:31 ` Rafael J. Wysocki
0 siblings, 0 replies; 3+ messages in thread
From: Rafael J. Wysocki @ 2016-04-04 1:31 UTC (permalink / raw)
To: Philippe Longepe, Linux PM list
Cc: Srinivas Pandruvada, Linux Kernel Mailing List
On Friday, April 01, 2016 09:44:43 AM Philippe Longepe wrote:
> I proposed also to simplify the intel_pstate_calc_busy function:
>
> core_pct = int_tofp(sample->aperf) * int_tofp(100);
> core_pct = div64_u64(core_pct, int_tofp(sample->mperf));
>
> is equivalent to:
>
> core_pct = sample->aperf * int_tofp(100);
> core_pct = div64_u64(core_pct, sample->mperf);
Right, this can be done too.
---
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Subject: [PATCH] intel_pstate: Avoid pointless FRAC_BITS shifts under div_fp()
There are multiple places in intel_pstate where int_tofp() is applied
to both arguments of div_fp(), but this is pointless, because int_tofp()
simply shifts its argument to the left by FRAC_BITS which mathematically
is equivalent to multuplication by 2^FRAC_BITS, so if this is done
to both arguments of a division, the extra factors will cancel each
other during that operation anyway.
Drop the pointless int_tofp() applied to div_fp() arguments throughout
the driver.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/cpufreq/intel_pstate.c | 31 +++++++++++++------------------
1 file changed, 13 insertions(+), 18 deletions(-)
Index: linux-pm/drivers/cpufreq/intel_pstate.c
===================================================================
--- linux-pm.orig/drivers/cpufreq/intel_pstate.c
+++ linux-pm/drivers/cpufreq/intel_pstate.c
@@ -206,17 +206,17 @@ static inline void pid_reset(struct _pid
static inline void pid_p_gain_set(struct _pid *pid, int percent)
{
- pid->p_gain = div_fp(int_tofp(percent), int_tofp(100));
+ pid->p_gain = div_fp(percent, 100);
}
static inline void pid_i_gain_set(struct _pid *pid, int percent)
{
- pid->i_gain = div_fp(int_tofp(percent), int_tofp(100));
+ pid->i_gain = div_fp(percent, 100);
}
static inline void pid_d_gain_set(struct _pid *pid, int percent)
{
- pid->d_gain = div_fp(int_tofp(percent), int_tofp(100));
+ pid->d_gain = div_fp(percent, 100);
}
static signed int pid_calc(struct _pid *pid, int32_t busy)
@@ -394,7 +394,7 @@ static ssize_t show_turbo_pct(struct kob
total = cpu->pstate.turbo_pstate - cpu->pstate.min_pstate + 1;
no_turbo = cpu->pstate.max_pstate - cpu->pstate.min_pstate + 1;
- turbo_fp = div_fp(int_tofp(no_turbo), int_tofp(total));
+ turbo_fp = div_fp(no_turbo, total);
turbo_pct = 100 - fp_toint(mul_fp(turbo_fp, int_tofp(100)));
return sprintf(buf, "%u\n", turbo_pct);
}
@@ -465,8 +465,7 @@ static ssize_t store_max_perf_pct(struct
limits->max_perf_pct);
limits->max_perf_pct = max(limits->min_perf_pct,
limits->max_perf_pct);
- limits->max_perf = div_fp(int_tofp(limits->max_perf_pct),
- int_tofp(100));
+ limits->max_perf = div_fp(limits->max_perf_pct, 100);
if (hwp_active)
intel_pstate_hwp_set_online_cpus();
@@ -490,8 +489,7 @@ static ssize_t store_min_perf_pct(struct
limits->min_perf_pct);
limits->min_perf_pct = min(limits->max_perf_pct,
limits->min_perf_pct);
- limits->min_perf = div_fp(int_tofp(limits->min_perf_pct),
- int_tofp(100));
+ limits->min_perf = div_fp(limits->min_perf_pct, 100);
if (hwp_active)
intel_pstate_hwp_set_online_cpus();
@@ -876,8 +874,8 @@ static inline void intel_pstate_calc_bus
struct sample *sample = &cpu->sample;
int64_t core_pct;
- core_pct = int_tofp(sample->aperf) * int_tofp(100);
- core_pct = div64_u64(core_pct, int_tofp(sample->mperf));
+ core_pct = sample->aperf * int_tofp(100);
+ core_pct = div64_u64(core_pct, sample->mperf);
sample->core_pct_busy = (int32_t)core_pct;
}
@@ -980,8 +978,8 @@ static inline int32_t get_target_pstate_
* specified pstate.
*/
core_busy = cpu->sample.core_pct_busy;
- max_pstate = int_tofp(cpu->pstate.max_pstate_physical);
- current_pstate = int_tofp(cpu->pstate.current_pstate);
+ max_pstate = cpu->pstate.max_pstate_physical;
+ current_pstate = cpu->pstate.current_pstate;
core_busy = mul_fp(core_busy, div_fp(max_pstate, current_pstate));
/*
@@ -992,8 +990,7 @@ static inline int32_t get_target_pstate_
*/
duration_ns = cpu->sample.time - cpu->last_sample_time;
if ((s64)duration_ns > pid_params.sample_rate_ns * 3) {
- sample_ratio = div_fp(int_tofp(pid_params.sample_rate_ns),
- int_tofp(duration_ns));
+ sample_ratio = div_fp(pid_params.sample_rate_ns, duration_ns);
core_busy = mul_fp(core_busy, sample_ratio);
}
@@ -1176,10 +1173,8 @@ static int intel_pstate_set_policy(struc
/* Make sure min_perf_pct <= max_perf_pct */
limits->min_perf_pct = min(limits->max_perf_pct, limits->min_perf_pct);
- limits->min_perf = div_fp(int_tofp(limits->min_perf_pct),
- int_tofp(100));
- limits->max_perf = div_fp(int_tofp(limits->max_perf_pct),
- int_tofp(100));
+ limits->min_perf = div_fp(limits->min_perf_pct, 100);
+ limits->max_perf = div_fp(limits->max_perf_pct, 100);
out:
intel_pstate_set_update_util_hook(policy->cpu);
^ permalink raw reply [flat|nested] 3+ messages in thread
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2016-03-31 13:46 [PATCH] intel_pstate: Avoid pointless FRAC_BITS shifts under div_fp() Rafael J. Wysocki
2016-04-01 7:44 ` Philippe Longepe
2016-04-04 1:31 ` Rafael J. Wysocki
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