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SubjectRe: [PATCH V5 09/12] perf: make events stream always parsable
On Tue, Jul 16, 2013 at 09:49:31AM +0300, Adrian Hunter wrote:

> If you want the ID at the first position in the ID sample, it is do-able.
> It means perf tools will have to be changed to calculate the variable start
> position of the ID sample, and then parse the ID sample forwards from there.
> Please advise.

Oh urgh I see.. how about I merge something like the below first?

Re-reading your patch; you add something to struct sample_id; which means that
events which 'forget' to set perf_event_attr::sample_id_all while setting
PERF_SAMPLE_IDENTIFIER are 'funny'. Should we refuse them?


---
Subject: perf: Update perf_event_type documentation

Due to a discussion with Adrian I had a good look at the perf_event_type record
layout and found the documentation to be somewhat unclear.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
include/uapi/linux/perf_event.h | 21 +++++++++++++++++++--
kernel/events/core.c | 31 ++++++++++++++++---------------
2 files changed, 35 insertions(+), 17 deletions(-)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index 0b1df41..335016c 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -478,6 +478,16 @@ enum perf_event_type {
* file will be supported by older perf tools, with these new optional
* fields being ignored.
*
+ * struct sample_id {
+ * { u32 pid, tid; } && PERF_SAMPLE_TID
+ * { u64 time; } && PERF_SAMPLE_TIME
+ * { u64 id; } && PERF_SAMPLE_ID
+ * { u64 stream_id;} && PERF_SAMPLE_STREAM_ID
+ * { u32 cpu, res; } && PERF_SAMPLE_CPU
+ * } && perf_event_attr::sample_id_all
+ */
+
+ /*
* The MMAP events record the PROT_EXEC mappings so that we can
* correlate userspace IPs to code. They have the following structure:
*
@@ -488,7 +498,8 @@ enum perf_event_type {
* u64 addr;
* u64 len;
* u64 pgoff;
+ * struct sample_id sample_id;
* };
*/
PERF_RECORD_MMAP = 1,
@@ -498,6 +509,7 @@ enum perf_event_type {
* struct perf_event_header header;
* u64 id;
* u64 lost;
+ * struct sample_id sample_id;
* };
*/
PERF_RECORD_LOST = 2,
@@ -508,6 +520,7 @@ enum perf_event_type {
*
* u32 pid, tid;
* char comm[];
+ * struct sample_id sample_id;
* };
*/
PERF_RECORD_COMM = 3,
@@ -518,6 +531,7 @@ enum perf_event_type {
* u32 pid, ppid;
* u32 tid, ptid;
* u64 time;
+ * struct sample_id sample_id;
* };
*/
PERF_RECORD_EXIT = 4,
@@ -528,6 +542,7 @@ enum perf_event_type {
* u64 time;
* u64 id;
* u64 stream_id;
+ * struct sample_id sample_id;
* };
*/
PERF_RECORD_THROTTLE = 5,
@@ -539,6 +554,7 @@ enum perf_event_type {
* u32 pid, ppid;
* u32 tid, ptid;
* u64 time;
+ * struct sample_id sample_id;
* };
*/
PERF_RECORD_FORK = 7,
@@ -549,6 +565,7 @@ enum perf_event_type {
* u32 pid, tid;
*
* struct read_format values;
+ * struct sample_id sample_id;
* };
*/
PERF_RECORD_READ = 8,
@@ -596,7 +613,7 @@ enum perf_event_type {
* u64 dyn_size; } && PERF_SAMPLE_STACK_USER
*
* { u64 weight; } && PERF_SAMPLE_WEIGHT
- * { u64 data_src; } && PERF_SAMPLE_DATA_SRC
+ * { u64 data_src; } && PERF_SAMPLE_DATA_SRC
* };
*/
PERF_RECORD_SAMPLE = 9,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 708ab70..c9ef899 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -4462,20 +4462,6 @@ void perf_output_sample(struct perf_output_handle *handle,
}
}

- if (!event->attr.watermark) {
- int wakeup_events = event->attr.wakeup_events;
-
- if (wakeup_events) {
- struct ring_buffer *rb = handle->rb;
- int events = local_inc_return(&rb->events);
-
- if (events >= wakeup_events) {
- local_sub(wakeup_events, &rb->events);
- local_inc(&rb->wakeup);
- }
- }
- }
-
if (sample_type & PERF_SAMPLE_BRANCH_STACK) {
if (data->br_stack) {
size_t size;
@@ -4511,16 +4497,31 @@ void perf_output_sample(struct perf_output_handle *handle,
}
}

- if (sample_type & PERF_SAMPLE_STACK_USER)
+ if (sample_type & PERF_SAMPLE_STACK_USER) {
perf_output_sample_ustack(handle,
data->stack_user_size,
data->regs_user.regs);
+ }

if (sample_type & PERF_SAMPLE_WEIGHT)
perf_output_put(handle, data->weight);

if (sample_type & PERF_SAMPLE_DATA_SRC)
perf_output_put(handle, data->data_src.val);
+
+ if (!event->attr.watermark) {
+ int wakeup_events = event->attr.wakeup_events;
+
+ if (wakeup_events) {
+ struct ring_buffer *rb = handle->rb;
+ int events = local_inc_return(&rb->events);
+
+ if (events >= wakeup_events) {
+ local_sub(wakeup_events, &rb->events);
+ local_inc(&rb->wakeup);
+ }
+ }
+ }
}

void perf_prepare_sample(struct perf_event_header *header,


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