Messages in this thread | | | Subject | Re: [PATCH 4/4] cpufreq: intel_pstate: enable boost for Skylake Xeon | From | Srinivas Pandruvada <> | Date | Mon, 30 Jul 2018 06:38:46 -0700 |
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Hi Eero, On Mon, 2018-07-30 at 11:33 +0300, Eero Tamminen wrote: > Hi, > > On 28.07.2018 17:14, Srinivas Pandruvada wrote: > > On Fri, 2018-07-27 at 22:34 -0700, Francisco Jerez wrote: > > > Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com> writes: > > > > > > > Enable HWP boost on Skylake server and workstations. > > > > > > > > > > Please revert this series, it led to significant energy usage and > > > graphics performance regressions [1]. > > > > Which SKX platform is targeted to graphics? > > Patch that Chris pointed out is this: > +static const struct x86_cpu_id intel_pstate_hwp_boost_ids[] = { > + ICPU(INTEL_FAM6_SKYLAKE_X, core_funcs), > + ICPU(INTEL_FAM6_SKYLAKE_DESKTOP, core_funcs), > + {} > +}; > > The regressing platforms in our test system were: > - SKL 6600K i5 / GT2 > - SKL 6770HQ i7 / GT4e > > SKL-U i5 / GT3e device wasn't impacted, so I assume U devices don't > match INTEL_FAM6_SKYLAKE_DESKTOP.
I have updated some steps in the bugzilla. Can you try that? Also add one workload which will show this issue immediately including any parameters you need to add.
Thanks, Srinivas
> > > > - Eero > > > > The reasons are roughly the ones > > > we discussed by e-mail off-list last April: This causes the > > > intel_pstate > > > driver to decrease the EPP to zero > > > > No. You didn't check this series. We are not using EPP at all. > > The boost mechanism used here is not boost to max. > > > > Thanks, > > Srinivas > > > > > when the workload blocks on IO > > > frequently enough, which for the regressing benchmarks detailed > > > in > > > [1] > > > is a symptom of the workload being heavily IO-bound, which means > > > they > > > won't benefit at all from the EPP boost since they aren't > > > significantly > > > CPU-bound, and they will suffer a decrease in parallelism due to > > > the > > > active CPU core using a larger fraction of the TDP in order to > > > achieve > > > the same work, causing the GPU to have a lower power budget > > > available, > > > leading to a decrease in system performance. > > > > > > You may want to give a shot to my previous suggestion of using > > > [2] in > > > order to detect whether the system is IO-bound, which you can use > > > as > > > an > > > indicator that the optimization implemented in this series cannot > > > possibly improve performance and can be expected to hurt energy > > > usage. > > > > > > Thanks. > > > > > > [1] https://bugs.freedesktop.org/show_bug.cgi?id=107410 > > > [2] https://patchwork.kernel.org/patch/10312259/ > > > > > > > Reported-by: Mel Gorman <mgorman@techsingularity.net> > > > > Tested-by: Giovanni Gherdovich <ggherdovich@suse.cz> > > > > Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.i > > > > ntel > > > > .com> > > > > --- > > > > drivers/cpufreq/intel_pstate.c | 10 ++++++++++ > > > > 1 file changed, 10 insertions(+) > > > > > > > > diff --git a/drivers/cpufreq/intel_pstate.c > > > > b/drivers/cpufreq/intel_pstate.c > > > > index 70bf63bb4e0e..01c8da1f99db 100644 > > > > --- a/drivers/cpufreq/intel_pstate.c > > > > +++ b/drivers/cpufreq/intel_pstate.c > > > > @@ -1794,6 +1794,12 @@ static const struct x86_cpu_id > > > > intel_pstate_cpu_ee_disable_ids[] = { > > > > {} > > > > }; > > > > > > > > +static const struct x86_cpu_id intel_pstate_hwp_boost_ids[] > > > > __initconst = { > > > > + ICPU(INTEL_FAM6_SKYLAKE_X, core_funcs), > > > > + ICPU(INTEL_FAM6_SKYLAKE_DESKTOP, core_funcs), > > > > + {} > > > > +}; > > > > + > > > > static int intel_pstate_init_cpu(unsigned int cpunum) > > > > { > > > > struct cpudata *cpu; > > > > @@ -1824,6 +1830,10 @@ static int > > > > intel_pstate_init_cpu(unsigned > > > > int cpunum) > > > > intel_pstate_disable_ee(cpunum); > > > > > > > > intel_pstate_hwp_enable(cpu); > > > > + > > > > + id = > > > > x86_match_cpu(intel_pstate_hwp_boost_ids); > > > > + if (id) > > > > + hwp_boost = true; > > > > } > > > > > > > > intel_pstate_get_cpu_pstates(cpu); > > > > -- > > > > 2.13.6 > >
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