linux-kernel - Re: [PATCH v4 5/7] powerpc/powernv: add event attribute and group to nest pmu

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Message-ID: <20150708224320.GC22635@us.ibm.com>
Date:	Wed, 8 Jul 2015 15:43:20 -0700
From:	Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
To:	Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
Cc:	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	Michael Ellerman <mpe@...erman.id.au>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Anton Blanchard <anton@...ba.org>,
	Anshuman Khandual <khandual@...ux.vnet.ibm.com>,
	Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH v4 5/7] powerpc/powernv: add event attribute and group to
 nest pmu

Madhavan Srinivasan [maddy@...ux.vnet.ibm.com] wrote:
| Add code to create event/format attributes and attribute groups for
| each nest pmu.
| 
| Cc: Michael Ellerman <mpe@...erman.id.au>
| Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
| Cc: Paul Mackerras <paulus@...ba.org>
| Cc: Anton Blanchard <anton@...ba.org>
| Cc: Sukadev Bhattiprolu <sukadev@...ux.vnet.ibm.com>
| Cc: Anshuman Khandual <khandual@...ux.vnet.ibm.com>
| Cc: Stephane Eranian <eranian@...gle.com>
| Signed-off-by: Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>
| ---
|  arch/powerpc/perf/nest-pmu.c | 57 ++++++++++++++++++++++++++++++++++++++++++++
|  1 file changed, 57 insertions(+)
| 
| diff --git a/arch/powerpc/perf/nest-pmu.c b/arch/powerpc/perf/nest-pmu.c
| index 6116ff3..20ed9f8 100644
| --- a/arch/powerpc/perf/nest-pmu.c
| +++ b/arch/powerpc/perf/nest-pmu.c
| @@ -13,6 +13,17 @@
|  static struct perchip_nest_info p8_nest_perchip_info[P8_NEST_MAX_CHIPS];
|  static struct nest_pmu *per_nest_pmu_arr[P8_NEST_MAX_PMUS];
| 
| +PMU_FORMAT_ATTR(event, "config:0-20");
| +struct attribute *p8_nest_format_attrs[] = {

name collision unlikely, but could this be static struct?

| +	&format_attr_event.attr,
| +	NULL,
| +};
| +
| +struct attribute_group p8_nest_format_group = {

static struct?

| +	.name = "format",
| +	.attrs = p8_nest_format_attrs,
| +};
| +
|  static int nest_event_info(struct property *pp, char *start,
|  			struct nest_ima_events *p8_events, int flg, u32 val)
|  {
| @@ -45,6 +56,48 @@ static int nest_event_info(struct property *pp, char *start,
|  	return 0;
|  }
| 
| +/*
| + * Populate event name and string in attribute
| + */
| +struct attribute *dev_str_attr(const char *name, const char *str)

static function?

| +{
| +	struct perf_pmu_events_attr *attr;
| +
| +	attr = kzalloc(sizeof(*attr), GFP_KERNEL);
| +

We recently needed following in 24x7 counters to keep lockdep happy:

	sysfs_attr_init(&attr->attr.attr);

| +	attr->event_str = str;
| +	attr->attr.attr.name = name;
| +	attr->attr.attr.mode = 0444;
| +	attr->attr.show = perf_event_sysfs_show;
| +
| +	return &attr->attr.attr;
| +}
| +
| +int update_events_in_group(

static function?

nit: do we need a new line before the first parameter? some functions
in the file don't add the new line.

| +	struct nest_ima_events *p8_events, int nevents, struct nest_pmu *pmu)

s/idx/nevents/?

| +{
| +	struct attribute_group *attr_group;
| +	struct attribute **attrs;
| +	int i;
| +
| +	/* Allocate memory for event attribute group */
| +	attr_group = kzalloc(((sizeof(struct attribute *) * (idx + 1)) +
| +				sizeof(*attr_group)), GFP_KERNEL);
| +	if (!attr_group)
| +		return -ENOMEM;
| +
| +	attrs = (struct attribute **)(attr_group + 1);

Can you add a comment on the +1?

| +	attr_group->name = "events";
| +	attr_group->attrs = attrs;
| +
| +	for (i = 0; i < idx; i++, p8_events++)
| +		attrs[i] = dev_str_attr((char *)p8_events->ev_name,
| +					(char *)p8_events->ev_value);
| +
| +	pmu->attr_groups[0] = attr_group;

The ->attr_groups[0] is initialized here, after the ->attr_groups[1] and
attr_groups[2] are initialized in caller. Since, ->attr_groups[1] and
->attr_groups[2] are set to global (loop-invariant) values, can we
initialize all the attribute-groups here? May need to rename function.

| +	return 0;
| +}
| +
|  static int nest_pmu_create(struct device_node *dev, int pmu_index)
|  {
|  	struct nest_ima_events **p8_events_arr, *p8_events;
| @@ -91,6 +144,7 @@ static int nest_pmu_create(struct device_node *dev, int pmu_index)
|  			/* Save the name to register it later */
|  			sprintf(buf, "Nest_%s", (char *)pp->value);
|  			pmu_ptr->pmu.name = (char *)buf;
| +			pmu_ptr->attr_groups[1] = &p8_nest_format_group;
|  			continue;
|  		}
| 
| @@ -122,6 +176,9 @@ static int nest_pmu_create(struct device_node *dev, int pmu_index)
|  		idx++;
|  	}
| 
| +	update_events_in_group(

nit: need newline before first param?

| +		(struct nest_ima_events *)p8_events_arr, idx, pmu_ptr);
| +
|  	return 0;
|  }
| 
| -- 
| 1.9.1

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