Re: [RFC PATCH v9 5/7] perf: cavium: Support memory controller PMU counters

[Jan Glauber]

On Wed, Aug 30, 2017 at 11:03:00AM +0100, Suzuki K Poulose wrote:
> On 29/08/17 14:12, Jan Glauber wrote:
> >Add support for the PMU counters on Cavium SOC memory controllers.
> >
> >This patch also adds generic functions to allow supporting more
> >devices with PMU counters.
> >
> >Properties of the LMC PMU counters:
> >- not stoppable
> >- fixed purpose
> >- read-only
> >- one PCI device per memory controller
> >
> >Signed-off-by: Jan Glauber <jglauber@xxxxxxxxxx>
> 
> Jan,
> 
> Some minor comments below.
> 
> >+static void cvm_pmu_del(struct perf_event *event, int flags)
> >+{
> >+	struct cvm_pmu_dev *pmu_dev = to_pmu_dev(event->pmu);
> >+	struct hw_perf_event *hwc = &event->hw;
> >+	int i;
> >+
> >+	event->pmu->stop(event, PERF_EF_UPDATE);
> >+
> >+	/*
> >+	 * For programmable counters we need to check where we installed it.
> >+	 * To keep this function generic always test the more complicated
> >+	 * case (free running counters won't need the loop).
> >+	 */
> >+	for (i = 0; i < pmu_dev->num_counters; i++)
> >+		if (cmpxchg(&pmu_dev->events[i], event, NULL) == event)
> >+			break;
> 
> Does this mean, it is the only way to map any given event (for programmable counters)
> to a hardware counter ? What do we store in hwc->idx ? We have 2 additional
> struct hw_perf_event_extra fields. We should be able to use one field to map it
> back to the counter, isn't it ?

Hmm, I might be able to use hwc-idx directly instead of the loop, will
check that.

> >+
> >+	perf_event_update_userpage(event);
> >+	hwc->idx = -1;
> >+}
> >+
> 
> ...
> 
> >+/* LMC events */
> >+#define LMC_EVENT_IFB_CNT		0x1d0
> >+#define LMC_EVENT_OPS_CNT		0x1d8
> >+#define LMC_EVENT_DCLK_CNT		0x1e0
> >+#define LMC_EVENT_BANK_CONFLICT1	0x360
> >+#define LMC_EVENT_BANK_CONFLICT2	0x368
> >+
> >+#define CVM_PMU_LMC_EVENT_ATTR(_name, _id)						\
> >+	&((struct perf_pmu_events_attr[]) {						\
> >+		{									\
> >+			__ATTR(_name, S_IRUGO, cvm_pmu_event_sysfs_show, NULL),		\
> >+			_id,								\
> >+			"lmc_event=" __stringify(_id),					\
> >+		}									\
> >+	})[0].attr.attr
> >+
> >+/* map counter numbers to register offsets */
> >+static int lmc_events[] = {
> >+	LMC_EVENT_IFB_CNT,
> >+	LMC_EVENT_OPS_CNT,
> >+	LMC_EVENT_DCLK_CNT,
> >+	LMC_EVENT_BANK_CONFLICT1,
> >+	LMC_EVENT_BANK_CONFLICT2,
> >+};
> >+
> >+static int cvm_pmu_lmc_add(struct perf_event *event, int flags)
> >+{
> >+	struct hw_perf_event *hwc = &event->hw;
> >+
> >+	return cvm_pmu_add(event, flags, LMC_CONFIG_OFFSET,
> >+			   lmc_events[hwc->config]);
> >+}
> >+
> 
> Is there any reason why we can't use the LMC event code directly
> here, avoiding the mapping altogether ?

I wanted to avoid exposing the raw numbers (0x1d0 - 0x368) here.

thanks,
Jan

> >+PMU_FORMAT_ATTR(lmc_event, "config:0-2");
> >+
> >+static struct attribute *cvm_pmu_lmc_format_attr[] = {
> >+	&format_attr_lmc_event.attr,
> >+	NULL,
> >+};
> >+
> >+static struct attribute_group cvm_pmu_lmc_format_group = {
> >+	.name = "format",
> >+	.attrs = cvm_pmu_lmc_format_attr,
> >+};
> >+
> >+static struct attribute *cvm_pmu_lmc_events_attr[] = {
> >+	CVM_PMU_LMC_EVENT_ATTR(ifb_cnt,		0),
> >+	CVM_PMU_LMC_EVENT_ATTR(ops_cnt,		1),
> >+	CVM_PMU_LMC_EVENT_ATTR(dclk_cnt,	2),
> >+	CVM_PMU_LMC_EVENT_ATTR(bank_conflict1,	3),
> >+	CVM_PMU_LMC_EVENT_ATTR(bank_conflict2,	4),
> >+	NULL,
> >+};