linux-kernel - Re: [PATCH v2 08/11] powerpc/perf: add support for the hv gpci (get performance counter info) interface

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Date:	Tue, 25 Feb 2014 13:25:34 -0800
From:	Cody P Schafer <cody@...ux.vnet.ibm.com>
To:	Michael Ellerman <mpe@...erman.id.au>,
	Linux PPC <linuxppc-dev@...ts.ozlabs.org>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Ingo Molnar <mingo@...hat.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Subject: Re: [PATCH v2 08/11] powerpc/perf: add support for the hv gpci (get
 performance counter info) interface

On 02/24/2014 07:33 PM, Michael Ellerman wrote:
> On Fri, 2014-14-02 at 22:02:12 UTC, Cody P Schafer wrote:
>> This provides a basic link between perf and hv_gpci. Notably, it does
>> not yet support transactions and does not list any events (they can
>> still be manually composed).
>
> Can you explain how the HV_CAPS stuff ends up looking.
>
> I'm not against adding it, but I'd like to understand how we expect it to be
> used a bit better.

It's just a quick mechanism for me to expose some relevant information 
to userspace via sysfs using the hv_perf_caps_get() function's returned 
data. Documentation for this sysfs interface (and the rest) is in a 
later patch.
I don't expect any more uses to show up unless the firmware decides to 
add another capability bit (in which case I'll want to expose it as well).

>> diff --git a/arch/powerpc/perf/hv-gpci.c b/arch/powerpc/perf/hv-gpci.c
>> new file mode 100644
>> index 0000000..1f5d96d
>> --- /dev/null
>> +++ b/arch/powerpc/perf/hv-gpci.c
>> +
>> +static struct pmu h_gpci_pmu = {
>> +	.task_ctx_nr = perf_invalid_context,
>> +
>> +	.name = "hv_gpci",
>> +	.attr_groups = attr_groups,
>> +	.event_init  = h_gpci_event_init,
>> +	.add         = h_gpci_event_add,
>> +	.del         = h_gpci_event_del,
> 		     = h_gpci_event_stop,
>
>> +	.start       = h_gpci_event_start,
>> +	.stop        = h_gpci_event_stop,
>> +	.read        = h_gpci_event_read,
> 		     = h_gpci_event_update
>
>> +	.event_idx = perf_swevent_event_idx,
>> +};

whoops, thought I had fixed those 2 already.

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