On 01/07/13 22:10, Stephane Eranian wrote:
> On Mon, Jul 1, 2013 at 8:53 PM, David Ahern <dsah...@gmail.com> wrote:
>>
>> On 7/1/13 3:32 AM, Adrian Hunter wrote:
>>>
>>> Snip
>>>
>>>>
>>>> While this works for a combined S/W and tracepoint events session, I do not
>>>> like promoting sample types to the minimum compatible level for all events
>>>> in the session. perf needs to allow each event to have its own sample_type
>>>> and not force a minimal compatibility.
>>>
>>>
>>> Why? The impact is small. The kernel API is completely unchanged.
>>
>>
>> I'd like to see libperf become a stable, usable library - usable by more
>> than the perf binary and its builtin commands. I have already done this once
>> for a daemon, and it was a PITA to get the specific use functional without
>> memory leaks/growth in the libperf part.
>>
>> With respect to this specific patch it means appropriate flexibility in the
>> data collected for events. ie., each event can have its own sample_type. For
>> example if the tracepoint already contains task information TID is not
>> needed - and IP may not be wanted either. The code processing the samples
>> should not require all events to have some minimum data format - that just
>> wastes buffer space.
>>
> I agree. This kernel needs to allow for any bit combination on
> sample_type and yet provide enough info
> to parse the buffer in the case of multi-event sampling. This is
> kernel bug. Tools should not have to handle
> this. Because it'd have to be repeated for each tool.
>
> Later this week, I'll post a patch that address the kernel limitation.
But isn't it trivial. Just add a new sample type that puts the ID first.
Anyone using the new PERF_SAMPLE_IDENTIFIER gets the new ABI.
diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 0b1df41..6bb217e 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -134,8 +134,9 @@ enum perf_event_sample_format {
PERF_SAMPLE_STACK_USER = 1U << 13,
PERF_SAMPLE_WEIGHT = 1U << 14,
PERF_SAMPLE_DATA_SRC = 1U << 15,
+ PERF_SAMPLE_IDENTIFIER = 1U << 16,
- PERF_SAMPLE_MAX = 1U << 16, /* non-ABI */
+ PERF_SAMPLE_MAX = 1U << 17, /* non-ABI */
};
/*
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 1db3af9..a3707af 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -1203,6 +1203,9 @@ static void perf_event__id_header_size(struct perf_event
*event)
if (sample_type & PERF_SAMPLE_TIME)
size += sizeof(data->time);
+ if (sample_type & PERF_SAMPLE_IDENTIFIER)
+ size += sizeof(data->id);
+
if (sample_type & PERF_SAMPLE_ID)
size += sizeof(data->id);
@@ -4229,7 +4232,7 @@ static void __perf_event_header__init_id(struct
perf_event_header *header,
if (sample_type & PERF_SAMPLE_TIME)
data->time = perf_clock();
- if (sample_type & PERF_SAMPLE_ID)
+ if (sample_type & (PERF_SAMPLE_ID | PERF_SAMPLE_IDENTIFIER))
data->id = primary_event_id(event);
if (sample_type & PERF_SAMPLE_STREAM_ID)
@@ -4268,6 +4271,9 @@ static void __perf_event__output_id_sample(struct
perf_output_handle *handle,
if (sample_type & PERF_SAMPLE_CPU)
perf_output_put(handle, data->cpu_entry);
+
+ if (sample_type & PERF_SAMPLE_IDENTIFER)
+ perf_output_put(handle, data->id);
}
void perf_event__output_id_sample(struct perf_event *event,
@@ -4380,6 +4386,9 @@ void perf_output_sample(struct perf_output_handle *handle,
perf_output_put(handle, *header);
+ if (sample_type & PERF_SAMPLE_IDENTIFIER)
+ perf_output_put(handle, data->id);
+
if (sample_type & PERF_SAMPLE_IP)
perf_output_put(handle, data->ip);
--
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