Re: [PATCH v1 4/9]powerpc/powernv: Add generic nest pmu ops

[Madhavan Srinivasan]

On Wednesday 03 June 2015 05:33 AM, Daniel Axtens wrote:
> On Tue, 2015-06-02 at 21:29 +0530, Madhavan Srinivasan wrote:
> > Patch adds generic nest pmu functions and format attribute.
> I'm not sure this commit message accurately reflects the content of the
> patch. At any rate, please could you:
>   - say what the patch adds the functions and attributes to.
>   - phrase your message as "Add generic ..." not "Patch adds
> generic ...": see
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/SubmittingPatches#n155
I will rephrase the commit message.

> >   
> > +PMU_FORMAT_ATTR(event, "config:0-20");
> > +struct attribute *p8_nest_format_attrs[] = {
> > +	&format_attr_event.attr,
> > +	NULL,
> > +};
> > +
> > +struct attribute_group p8_nest_format_group = {
> > +	.name = "format",
> > +	.attrs = p8_nest_format_attrs,
> > +};
> Can these structs be constified?
I guess so. Will try it out.

> > +
> > +int p8_nest_event_init(struct perf_event *event)
> > +{
> > +	int chip_id;
> > +
> > +	if (event->attr.type != event->pmu->type)
> > +		return -ENOENT;
> > +
> > +	/* Sampling not supported yet */
> > +	if (event->hw.sample_period)
> > +		return -EINVAL;
> > +
> > +	/* unsupported modes and filters */
> > +	if (event->attr.exclude_user   ||
> > +	    event->attr.exclude_kernel ||
> > +	    event->attr.exclude_hv     ||
> > +	    event->attr.exclude_idle   ||
> > +	    event->attr.exclude_host   ||
> > +	    event->attr.exclude_guest  ||
> > +	    event->attr.sample_period) /* no sampling */
> > +		return -EINVAL;
> You test for sample period twice here.
My bad. Will remove it.

> > +
> > +	if (event->cpu < 0)
> > +		return -EINVAL;
> > +
> > +	chip_id = topology_physical_package_id(event->cpu);
> > +	event->hw.event_base = event->attr.config +
> > +				p8_perchip_nest_info[chip_id].vbase;
> > +
> > +	return 0;
> > +}
> > +
> > +void p8_nest_read_counter(struct perf_event *event)
> > +{
> > +	u64 *addr;
> > +	u64 data = 0;
> > +
> > +	addr = (u64 *)event->hw.event_base;
> > +	data = __be64_to_cpu((uint64_t)*addr);
> > +	local64_set(&event->hw.prev_count, data);
> > +}
> > +
> > +void p8_nest_perf_event_update(struct perf_event *event)
> > +{
> > +	u64 counter_prev, counter_new, final_count;
> > +	uint64_t *addr;
> > +
> > +	addr = (u64 *)event->hw.event_base;
> > +	counter_prev = local64_read(&event->hw.prev_count);
> > +	counter_new = __be64_to_cpu((uint64_t)*addr);
> > +	final_count = counter_new - counter_prev;
> > +
> > +	local64_set(&event->hw.prev_count, counter_new);
> > +	local64_add(final_count, &event->count);
> > +}
> > +
> > +void p8_nest_event_start(struct perf_event *event, int flags)
> > +{
> > +	event->hw.state = 0;
> > +	p8_nest_read_counter(event);
> > +}
> > +
> > +void p8_nest_event_stop(struct perf_event *event, int flags)
> > +{
> > +	p8_nest_perf_event_update(event);
> > +}
> > +
> > +int p8_nest_event_add(struct perf_event *event, int flags)
> > +{
> > +	p8_nest_event_start(event, flags);
> > +	return 0;
> > +}
> > +
> > +void p8_nest_event_del(struct perf_event *event, int flags)
> > +{
> > +	p8_nest_event_stop(event, flags);
> Is this necessary?
>
> Stop calls update, which I guess makes sense as it finalises the value.
> But if the event is being deleted anyway, why not just do nothing here?
IIUC, "perf record"  will use the event start/stop interface. Incase of 
"perf stat" (for PMUs which
does not support sampling), event add/del interface is used. Now when 
event is disable or deleted,
event count should get updated with the delta value.

> > +}
> > +
> Regards,
> Daniel Axtens
Thanks for the review
Maddy

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