On Tue, 2009-08-11 at 17:41 +0200, stephane eranian wrote:
> Hi,
>
> It seems to me there is a problem with the group counter values
> when you use PERF_SAMPLE_GROUP. The counts are bogus
> for all events.
>
> Test case is pretty simple:
> - single group, 2 events
> - sampling on PERF_COUNT_HW_CYCLES
> - other event is PERF_COUNT_HW_CYCLES
> - leader has SAMPLE_IP|SAMPLE_GROUP
> - no inheritance
> - single thread
> - using sampling in one shot mode with PERF_COUNTER_IOC_REFRESH
> - all events but leader start with disabled = 0 (i.e., enabled)
> - sampling period is 240000000 (cycles)
>
> Notification 1: ip=0x401300 39100608 PERF_COUNT_HW_CPU_CYCLES (12)
> Notification 2: ip=0x401300 17991616 PERF_COUNT_HW_CPU_CYCLES (12)
> Notification 3: ip=0x401300 17981248 PERF_COUNT_HW_CPU_CYCLES (12)
> Notification 4: ip=0x401300 9409478912 PERF_COUNT_HW_CPU_CYCLES (12)
>
> I would expect the value for the 2nd event to be close to 240000000.
> But instead,
> it is going up and down. The IP, nr and id (12) fields are correct, so
> the parsing of
> the buffer is correct. This is with the latest from Linus's 2.6.31-rc5.
Could have broken somewhere along the line, the group stuff doesn't get
tested a lot, if at all.
perf used to have some support for it, not sure what the current state
is.
You seem to have forgotten to append your test.c though :-)
> Related to PERF_SAMPLE_GROUP, I believe there is some information missing.
> You need to provide the TIMING information because in the case of SAMPLE_GROUP
> you'd like to be able to scale the values of the counters you are
> collecting. And you
> need the timing at the moment, the sample was recorded not later.
Right, so something like the below, possibly complemented with having
PERF_COUNTER_IOC_RESET also reset the run-times?
---
include/linux/perf_counter.h | 3 +++
kernel/perf_counter.c | 20 ++++++++++++++++++--
2 files changed, 21 insertions(+), 2 deletions(-)
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 2b36afe..44a056b 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -365,10 +365,13 @@ enum perf_event_type {
* { u64 period; } && PERF_SAMPLE_PERIOD
*
* { u64 nr;
+ * { u64 time_enabled; } && PERF_FORMAT_ENABLED
+ * { u64 time_running; } && PERF_FORMAT_RUNNING
* { u64 id, val; } cnt[nr]; } && PERF_SAMPLE_GROUP
*
* { u64 nr,
* u64 ips[nr]; } && PERF_SAMPLE_CALLCHAIN
+ *
* { u32 size;
* char data[size];}&& PERF_SAMPLE_RAW
* };
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index e26d2fc..e61e701 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -2636,6 +2636,7 @@ void perf_counter_output(struct perf_counter *counter,
int nmi,
{
int ret;
u64 sample_type = counter->attr.sample_type;
+ u64 read_format = counter->attr.read_format;
struct perf_output_handle handle;
struct perf_event_header header;
u64 ip;
@@ -2703,6 +2704,10 @@ void perf_counter_output(struct perf_counter *counter,
int nmi,
if (sample_type & PERF_SAMPLE_GROUP) {
header.size += sizeof(u64) +
counter->nr_siblings * sizeof(group_entry);
+ if (read_format & PERF_FORMAT_ENABLED)
+ header.size += sizeof(u64);
+ if (read_format & PERF_FORMAT_RUNNING)
+ header.size += sizeof(u64);
}
if (sample_type & PERF_SAMPLE_CALLCHAIN) {
@@ -2765,9 +2770,20 @@ void perf_counter_output(struct perf_counter *counter,
int nmi,
*/
if (sample_type & PERF_SAMPLE_GROUP) {
struct perf_counter *leader, *sub;
- u64 nr = counter->nr_siblings;
+ u64 val;
+
+ val = counter->nr_siblings;
+ perf_output_put(&handle, val);
- perf_output_put(&handle, nr);
+ if (read_format & PERF_FORMAT_ENABLED) {
+ val = counter->total_time_enabled;
+ perf_output_put(&handle, val);
+ }
+
+ if (read_format & PERF_FORMAT_RUNNING) {
+ val = counter->total_time_running;
+ perf_output_put(&handle, val);
+ }
leader = counter->group_leader;
list_for_each_entry(sub, &leader->sibling_list, list_entry) {
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