| Message ID | 1499729032-22038-1-git-send-email-srinivas.pandruvada@linux.intel.com (mailing list archive) |
|---|---|
| State | Mainlined |
| Delegated to: | Rafael Wysocki |
| Headers | show |
On Monday, July 10, 2017 04:23:52 PM Srinivas Pandruvada wrote: > When the minimum performance limit percentage is set to power-up default, > it is possible that minimum performance ratio is set to one more than the > desired. > > During set_policy() callback the minimum ratio is calculated by applying > global.min_perf_pct to the turbo_ratio and rounding up. But the power-up > default global.min_perf_pct is already rounded up to next percent in the > function min_perf_pct_min(). So this will result in two round up > operations. So for the default min_perf_pct, one of the rounding up is > not required. > > It is better to remove rounding up in min_perf_pct_min() as this matches > the displayed min_perf_pct prior to the > commit c5a2ee7dde89 ("cpufreq: intel_pstate: Active mode P-state limits > rework") in the kernel version 4,12. For example on a platform with > max turbo ratio of 37 and minimum ratio of 10, the min_perf_pct resulted > in 28 with the above commit. Before this commit it was 27 and same after > this change. > > Fixes: 1a4fe38add8b ("cpufreq: intel_pstate: Remove max/min fractions to > limit performance") > Reported-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> > Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> Applied, thanks!
diff --git a/drivers/cpufreq/intel_pstate.c b/drivers/cpufreq/intel_pstate.c index 48a98f11a84e..2a65bd313938 100644 --- a/drivers/cpufreq/intel_pstate.c +++ b/drivers/cpufreq/intel_pstate.c @@ -572,7 +572,7 @@ static int min_perf_pct_min(void) int turbo_pstate = cpu->pstate.turbo_pstate; return turbo_pstate ? - DIV_ROUND_UP(cpu->pstate.min_pstate * 100, turbo_pstate) : 0; + (cpu->pstate.min_pstate * 100 / turbo_pstate) : 0; } static s16 intel_pstate_get_epb(struct cpudata *cpu_data)
When the minimum performance limit percentage is set to power-up default, it is possible that minimum performance ratio is set to one more than the desired. During set_policy() callback the minimum ratio is calculated by applying global.min_perf_pct to the turbo_ratio and rounding up. But the power-up default global.min_perf_pct is already rounded up to next percent in the function min_perf_pct_min(). So this will result in two round up operations. So for the default min_perf_pct, one of the rounding up is not required. It is better to remove rounding up in min_perf_pct_min() as this matches the displayed min_perf_pct prior to the commit c5a2ee7dde89 ("cpufreq: intel_pstate: Active mode P-state limits rework") in the kernel version 4,12. For example on a platform with max turbo ratio of 37 and minimum ratio of 10, the min_perf_pct resulted in 28 with the above commit. Before this commit it was 27 and same after this change. Fixes: 1a4fe38add8b ("cpufreq: intel_pstate: Remove max/min fractions to limit performance") Reported-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> --- drivers/cpufreq/intel_pstate.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)