[PATCH v3 1/4] cpufreq: amd-pstate: Add more tracepoint for AMD P-State module

Jinzhou Su
2022-03-09T01:24:45Z

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>
---
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);
+ }

if (value == prev)
return;
--
2.27.0