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Date: Fri, 4 Mar 2022 19:49:51 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Huang Rui <ray.huang@....com>
Cc: "Su, Jinzhou (Joe)" <Jinzhou.Su@....com>,
"rjw@...ysocki.net" <rjw@...ysocki.net>,
"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
"srinivas.pandruvada@...ux.intel.com"
<srinivas.pandruvada@...ux.intel.com>,
"dsmythies@...us.net" <dsmythies@...us.net>,
"viresh.kumar@...aro.org" <viresh.kumar@...aro.org>,
"todd.e.brandt@...ux.intel.com" <todd.e.brandt@...ux.intel.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Sharma, Deepak" <Deepak.Sharma@....com>,
"Deucher, Alexander" <Alexander.Deucher@....com>,
"Du, Xiaojian" <Xiaojian.Du@....com>,
"Yuan, Perry" <Perry.Yuan@....com>,
"Meng, Li (Jassmine)" <Li.Meng@....com>
Subject: Re: [PATCH V2 1/4] cpufreq: amd-pstate: Add more tracepoint for AMD
P-State module
On Fri, Mar 4, 2022 at 7:42 AM Huang Rui <ray.huang@....com> wrote:
>
> On Fri, Mar 04, 2022 at 02:07:21PM +0800, Su, Jinzhou (Joe) wrote:
> > Add frequency, mperf, aperf and tsc in the trace. This can be used
> > to debug and tune the performance of AMD P-state driver.
> >
> > Use the time difference between amd_pstate_update to calculate CPU
> > frequency. There could be sleep in arch_freq_get_on_cpu, so do not
> > use it here.
> >
> > Signed-off-by: Jinzhou Su <Jinzhou.Su@....com>
> > Co-developed-by: Huang Rui <ray.huang@....com>
> > Signed-off-by: Huang Rui <ray.huang@....com>
>
> Let's remove "Signed-off-by" of me, just leave "Co-developed-by".
Actually, they both need to be present (the C-d-b clarifies the S-o-b
meaning), so the above is correct.
>
> > ---
> > drivers/cpufreq/amd-pstate-trace.h | 22 ++++++++++-
> > drivers/cpufreq/amd-pstate.c | 59 +++++++++++++++++++++++++++++-
> > 2 files changed, 78 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/cpufreq/amd-pstate-trace.h b/drivers/cpufreq/amd-pstate-trace.h
> > index 647505957d4f..35f38ae67fb1 100644
> > --- a/drivers/cpufreq/amd-pstate-trace.h
> > +++ b/drivers/cpufreq/amd-pstate-trace.h
> > @@ -27,6 +27,10 @@ TRACE_EVENT(amd_pstate_perf,
> > TP_PROTO(unsigned long min_perf,
> > unsigned long target_perf,
> > unsigned long capacity,
> > + u64 freq,
> > + u64 mperf,
> > + u64 aperf,
> > + u64 tsc,
> > unsigned int cpu_id,
> > bool changed,
> > bool fast_switch
> > @@ -35,6 +39,10 @@ TRACE_EVENT(amd_pstate_perf,
> > TP_ARGS(min_perf,
> > target_perf,
> > capacity,
> > + freq,
> > + mperf,
> > + aperf,
> > + tsc,
> > cpu_id,
> > changed,
> > fast_switch
> > @@ -44,6 +52,10 @@ TRACE_EVENT(amd_pstate_perf,
> > __field(unsigned long, min_perf)
> > __field(unsigned long, target_perf)
> > __field(unsigned long, capacity)
> > + __field(unsigned long long, freq)
> > + __field(unsigned long long, mperf)
> > + __field(unsigned long long, aperf)
> > + __field(unsigned long long, tsc)
> > __field(unsigned int, cpu_id)
> > __field(bool, changed)
> > __field(bool, fast_switch)
> > @@ -53,15 +65,23 @@ TRACE_EVENT(amd_pstate_perf,
> > __entry->min_perf = min_perf;
> > __entry->target_perf = target_perf;
> > __entry->capacity = capacity;
> > + __entry->freq = freq;
> > + __entry->mperf = mperf;
> > + __entry->aperf = aperf;
> > + __entry->tsc = tsc;
> > __entry->cpu_id = cpu_id;
> > __entry->changed = changed;
> > __entry->fast_switch = fast_switch;
> > ),
> >
> > - TP_printk("amd_min_perf=%lu amd_des_perf=%lu amd_max_perf=%lu cpu_id=%u changed=%s fast_switch=%s",
> > + TP_printk("amd_min_perf=%lu amd_des_perf=%lu amd_max_perf=%lu freq=%llu mperf=%llu aperf=%llu tsc=%llu cpu_id=%u changed=%s fast_switch=%s",
> > (unsigned long)__entry->min_perf,
> > (unsigned long)__entry->target_perf,
> > (unsigned long)__entry->capacity,
> > + (unsigned long long)__entry->freq,
> > + (unsigned long long)__entry->mperf,
> > + (unsigned long long)__entry->aperf,
> > + (unsigned long long)__entry->tsc,
> > (unsigned int)__entry->cpu_id,
> > (__entry->changed) ? "true" : "false",
> > (__entry->fast_switch) ? "true" : "false"
> > diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> > index 9ce75ed11f8e..7be38bc6a673 100644
> > --- a/drivers/cpufreq/amd-pstate.c
> > +++ b/drivers/cpufreq/amd-pstate.c
> > @@ -65,6 +65,18 @@ MODULE_PARM_DESC(shared_mem,
> >
> > static struct cpufreq_driver amd_pstate_driver;
> >
> > +/**
> > + * struct amd_aperf_mperf
> > + * @aperf: actual performance frequency clock count
> > + * @mperf: maximum performance frequency clock count
> > + * @tsc: time stamp counter
> > + */
> > +struct amd_aperf_mperf {
> > + u64 aperf;
> > + u64 mperf;
> > + u64 tsc;
> > +};
> > +
> > /**
> > * struct amd_cpudata - private CPU data for AMD P-State
> > * @cpu: CPU number
> > @@ -81,6 +93,9 @@ static struct cpufreq_driver amd_pstate_driver;
> > * @min_freq: the frequency that mapped to lowest_perf
> > * @nominal_freq: the frequency that mapped to nominal_perf
> > * @lowest_nonlinear_freq: the frequency that mapped to lowest_nonlinear_perf
> > + * @cur: Difference of Aperf/Mperf/tsc count between last and current sample
> > + * @prev: Last Aperf/Mperf/tsc count value read from register
> > + * @freq: current cpu frequency value
> > * @boost_supported: check whether the Processor or SBIOS supports boost mode
> > *
> > * The amd_cpudata is key private data for each CPU thread in AMD P-State, and
> > @@ -102,6 +117,10 @@ struct amd_cpudata {
> > u32 nominal_freq;
> > u32 lowest_nonlinear_freq;
> >
> > + struct amd_aperf_mperf cur;
> > + struct amd_aperf_mperf prev;
> > +
> > + u64 freq;
> > bool boost_supported;
> > };
> >
> > @@ -211,6 +230,39 @@ static inline void amd_pstate_update_perf(struct amd_cpudata *cpudata,
> > max_perf, fast_switch);
> > }
> >
> > +static inline bool amd_pstate_sample(struct amd_cpudata *cpudata)
> > +{
> > + u64 aperf, mperf, tsc;
> > + unsigned long flags;
> > +
> > + local_irq_save(flags);
> > + rdmsrl(MSR_IA32_APERF, aperf);
> > + rdmsrl(MSR_IA32_MPERF, mperf);
> > + tsc = rdtsc();
> > +
> > + if (cpudata->prev.mperf == mperf || cpudata->prev.tsc == tsc) {
> > + local_irq_restore(flags);
> > + return false;
> > + }
> > +
> > + local_irq_restore(flags);
> > +
> > + cpudata->cur.aperf = aperf;
> > + cpudata->cur.mperf = mperf;
> > + cpudata->cur.tsc = tsc;
> > + cpudata->cur.aperf -= cpudata->prev.aperf;
> > + cpudata->cur.mperf -= cpudata->prev.mperf;
> > + cpudata->cur.tsc -= cpudata->prev.tsc;
> > +
> > + cpudata->prev.aperf = aperf;
> > + cpudata->prev.mperf = mperf;
> > + cpudata->prev.tsc = tsc;
> > +
> > + cpudata->freq = div64_u64((cpudata->cur.aperf * cpu_khz), cpudata->cur.mperf);
> > +
> > + return true;
> > +}
> > +
> > static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
> > u32 des_perf, u32 max_perf, bool fast_switch)
> > {
> > @@ -226,8 +278,11 @@ static void amd_pstate_update(struct amd_cpudata *cpudata, u32 min_perf,
> > value &= ~AMD_CPPC_MAX_PERF(~0L);
> > value |= AMD_CPPC_MAX_PERF(max_perf);
> >
> > - trace_amd_pstate_perf(min_perf, des_perf, max_perf,
> > - cpudata->cpu, (value != prev), fast_switch);
> > + if (trace_amd_pstate_perf_enabled() && amd_pstate_sample(cpudata)) {
> > + trace_amd_pstate_perf(min_perf, des_perf, max_perf, cpudata->freq,
> > + cpudata->cur.mperf, cpudata->cur.aperf, cpudata->cur.tsc,
> > + cpudata->cpu, (value != prev), fast_switch);
>
> How about using struct amd_aperf_mperf pointer as one input:
>
> trace_amd_pstate_perf(min_perf, des_perf, max_perf, &cpudata->cur, ...);
>
> You can refer the members of struct amd_aperf_mperf in the
> amd-pstate-trace.h:
>
> __entry->mperf = cur->mperf;
> __entry->aperf = cur->aperf;
> __entry->tsc = cur->tsc;
>
> Thanks,
> Ray
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