Re: [PATCH 13/16] perf: Add a speculative page fault sw events

[Laurent Dufour]

On 09/08/2017 15:18, Michael Ellerman wrote:
> Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx> writes:
> 
>> Add new software events to count succeeded and failed speculative page
>> faults.
>>
>> Signed-off-by: Laurent Dufour <ldufour@xxxxxxxxxxxxxxxxxx>
>> ---
>>  include/uapi/linux/perf_event.h | 2 ++
>>  1 file changed, 2 insertions(+)
>>
>> diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
>> index b1c0b187acfe..fbfb03dff334 100644
>> --- a/include/uapi/linux/perf_event.h
>> +++ b/include/uapi/linux/perf_event.h
>> @@ -111,6 +111,8 @@ enum perf_sw_ids {
>>  	PERF_COUNT_SW_EMULATION_FAULTS		= 8,
>>  	PERF_COUNT_SW_DUMMY			= 9,
>>  	PERF_COUNT_SW_BPF_OUTPUT		= 10,
>> +	PERF_COUNT_SW_SPF_DONE			= 11,
>> +	PERF_COUNT_SW_SPF_FAILED		= 12,
> 
> Can't you calculate:
> 
>   PERF_COUNT_SW_SPF_FAILED = PERF_COUNT_SW_PAGE_FAULTS - PERF_COUNT_SW_SPF_DONE
> 
> ie. do you need a separate event for it?

Unfortunately not, because PERF_COUNT_SW_PAGE_FAULTS counts also page
faults from the kernel space, while SPF is only concerning user space page
faults.

Cheers,
Laurent.