Re: [PATCH V2 1/4] cpufreq: amd-pstate: Add more tracepoint for AMD P-State module

[Huang Rui <ray.huang@amd.com>]

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@amd.com>
> Co-developed-by: Huang Rui <ray.huang@amd.com>
> Signed-off-by: Huang Rui <ray.huang@amd.com>

Let's remove "Signed-off-by" of me, just leave "Co-developed-by".

> ---
>  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