Re: [RFC] perf/x86/rapl: Getting zero on energy-cores event

[Liang, Kan]

On 3/1/2019 6:42 AM, Jiri Olsa wrote:
hi,
I'm getting zero counts for energy-cores event on broadwell-x
server (model 0x4f)

I checked intel_rapl powercap driver and it won't export the
counter if it rdmsr returns zero on it

the SDM also says the rdmsr returns zero for some models

I made changes on perf rapl pmu below to remove sysfs events
if their rdmsr returns zero just to ilustrate the case

I think there's probably better fix, but I'm not sure if
there's a reason for zero counters to be exposed..?

+Stephane, who is the author.

I'm OK to hide the zero counters.



thoughts? thanks,
jirka


---
diff --git a/arch/x86/events/intel/rapl.c b/arch/x86/events/intel/rapl.c
index 94dc564146ca..effb9a9d2368 100644
--- a/arch/x86/events/intel/rapl.c
+++ b/arch/x86/events/intel/rapl.c
@@ -54,6 +54,7 @@
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <linux/perf_event.h>
+#include <linux/nospec.h>
  #include <asm/cpu_device_id.h>
  #include <asm/intel-family.h>
  #include "../perf_event.h"
@@ -346,10 +347,18 @@ static void rapl_pmu_event_del(struct perf_event *event, 
int flags)
        rapl_pmu_event_stop(event, PERF_EF_UPDATE);
  }
  
+static unsigned int event_msr[NR_RAPL_DOMAINS] = {
+       MSR_PP0_ENERGY_STATUS,
+       MSR_PKG_ENERGY_STATUS,
+       MSR_DRAM_ENERGY_STATUS,
+       MSR_PP1_ENERGY_STATUS,
+       MSR_PLATFORM_ENERGY_STATUS,
+};
+
  static int rapl_pmu_event_init(struct perf_event *event)
  {
        u64 cfg = event->attr.config & RAPL_EVENT_MASK;
-       int bit, msr, ret = 0;
+       int bit, ret = 0;
        struct rapl_pmu *pmu;
  
  	/* only look at RAPL events */
@@ -365,33 +374,12 @@ static int rapl_pmu_event_init(struct perf_event *event)
  
  	event->event_caps |= PERF_EV_CAP_READ_ACTIVE_PKG;
  
-	/*
-        * check event is known (determines counter)
-        */
-       switch (cfg) {
-       case INTEL_RAPL_PP0:
-               bit = RAPL_IDX_PP0_NRG_STAT;
-               msr = MSR_PP0_ENERGY_STATUS;
-               break;
-       case INTEL_RAPL_PKG:
-               bit = RAPL_IDX_PKG_NRG_STAT;
-               msr = MSR_PKG_ENERGY_STATUS;
-               break;
-       case INTEL_RAPL_RAM:
-               bit = RAPL_IDX_RAM_NRG_STAT;
-               msr = MSR_DRAM_ENERGY_STATUS;
-               break;
-       case INTEL_RAPL_PP1:
-               bit = RAPL_IDX_PP1_NRG_STAT;
-               msr = MSR_PP1_ENERGY_STATUS;
-               break;
-       case INTEL_RAPL_PSYS:
-               bit = RAPL_IDX_PSYS_NRG_STAT;
-               msr = MSR_PLATFORM_ENERGY_STATUS;
-               break;
-       default:
+       if (!cfg || cfg >= NR_RAPL_DOMAINS)
                return -EINVAL;
-       }
+
+       cfg = array_index_nospec(cfg, NR_RAPL_DOMAINS);
+       bit = cfg - 1;
+
        /* check event supported */
        if (!(rapl_cntr_mask & (1 << bit)))
                return -EINVAL;
@@ -406,7 +394,7 @@ static int rapl_pmu_event_init(struct perf_event *event)
                return -EINVAL;
        event->cpu = pmu->cpu;
        event->pmu_private = pmu;
-       event->hw.event_base = msr;
+       event->hw.event_base = event_msr[bit];
        event->hw.config = cfg;
        event->hw.idx = bit;
  
@@ -435,11 +423,27 @@ static struct attribute_group rapl_pmu_attr_group = {
        .attrs = rapl_pmu_attrs,
  };
  
-RAPL_EVENT_ATTR_STR(energy-cores, rapl_cores, "event=0x01");
-RAPL_EVENT_ATTR_STR(energy-pkg  ,   rapl_pkg, "event=0x02");
-RAPL_EVENT_ATTR_STR(energy-ram  ,   rapl_ram, "event=0x03");
-RAPL_EVENT_ATTR_STR(energy-gpu  ,   rapl_gpu, "event=0x04");
-RAPL_EVENT_ATTR_STR(energy-psys,   rapl_psys, "event=0x05");
+static ssize_t
+rapl_event_sysfs_show(struct device *dev, struct device_attribute *attr,
+                     char *page)
+{
+       struct perf_pmu_events_attr *pmu_attr =
+               container_of(attr, struct perf_pmu_events_attr, attr);
+
+       return sprintf(page, "event=%llu\n", pmu_attr->id);
+}
+
+#define RAPL_EVENT_ATTR(_name, v, _id)                                 \
+static struct perf_pmu_events_attr event_attr_##v = {                  \
+       .attr   = __ATTR(_name, 0444, rapl_event_sysfs_show, NULL),     \
+       .id     = RAPL_IDX_##_id##_NRG_STAT,                            \
+};
+
+RAPL_EVENT_ATTR(energy-cores,  rapl_cores,  PP0);
+RAPL_EVENT_ATTR(energy-pkg  ,    rapl_pkg,  PKG);
+RAPL_EVENT_ATTR(energy-ram  ,    rapl_ram,  RAM);
+RAPL_EVENT_ATTR(energy-gpu  ,    rapl_gpu,  PP1);
+RAPL_EVENT_ATTR(energy-psys ,   rapl_psys, PSYS);
  
  RAPL_EVENT_ATTR_STR(energy-cores.unit, rapl_cores_unit, "Joules");
  RAPL_EVENT_ATTR_STR(energy-pkg.unit  ,   rapl_pkg_unit, "Joules");
@@ -780,6 +784,59 @@ static const struct x86_cpu_id rapl_cpu_match[] 
__initconst = {
  
  MODULE_DEVICE_TABLE(x86cpu, rapl_cpu_match);
  
+static void __init remove_name(struct attribute **attrs, const char *name)
+{
+       struct device_attribute *attr;
+       int i, j;
+
+       for (i = 0; attrs[i]; i++) {
+               attr = (struct device_attribute *) attrs[i];
+
+               if (strncmp(name, attr->attr.name, strlen(name)))
+                       continue;
+
+               for (j = i; attrs[j]; j++)
+                       attrs[j] = attrs[j + 1];
+
+               /* Check the shifted attr. */
+               i--;
+       }
+}
+
+static void __init check_events(struct attribute **attrs)
+{
+       struct perf_pmu_events_attr *pmu_attr;
+       struct device_attribute *attr;
+       int i, j;
+
+       for (i = 0; attrs[i]; i++) {
+               u64 val = 0;
+               u64 bit;
+
+               attr     = (struct device_attribute *) attrs[i];
+               pmu_attr = container_of(attr, struct perf_pmu_events_attr, 
attr);
+
+               if (pmu_attr->event_str)
+                       continue;
+
+               bit = pmu_attr->id;
+
+               if (WARN_ON_ONCE(bit >= NR_RAPL_DOMAINS))
+                       continue;
+
+               if (!rdmsrl_safe(event_msr[bit], &val) && val)
+                       continue;
+
+               remove_name(&attrs[i + 1], attr->attr.name);

In perf cstate, we check and insert the available events for sysfs attrs
I think we should use the same way here. It's better to factor out a 
common function for both cstate and rapl.


Peter,

The cstate, rapl and uncore are similar. I think it should be the right 
direction to abstract several common functions for them.
Here, the sysfs attrs is an example.
The common topology related functions I proposed is another example.
https://lore.kernel.org/lkml/9631a92f-5b24-26a6-e160-4e4c0b469...@linux.intel.com/

Thanks,
Kan