On s390 the counter and sampling facility do not support a
precise IP skid level and sometimes returns EOPNOTSUPP when
structure member precise_ip in struct perf_event_attr
is not set to zero.
On s390 commnd 'perf record -- true' fails with error EOPNOTSUPP.
This happens only when no events are specified on command line.
The functions called are
...
--> perf_evlist__add_default
--> perf_evsel__new_cycles
--> perf_event_attr__set_max_precise_ip
The last function determines the value of structure member precise_ip
by invoking the perf_event_open() system call and checking the return code.
The first successful open is the value for precise_ip.
However the value is determined without setting member sample_period
and indicates no sampling.
On s390 the counter facility and sampling facility are different.
The above procedure determines a precise_ip value of 3 using the
counter facility. Later it uses the sampling facility with a value of 3
and fails with EOPNOTSUPP.
Fix this by changing function perf_evsel__new_cycles(). It is called
very early in the event setup. Delay the determination of
the value of precise_ip until the context is known. This is the case
when perf_evsel__config() is called.
Function perf_evsel__new_cycles() just marks precise_ip to be
determined later.
Also change the modifier to 'P' for maximum detected precise level.
Suggested-by: Hendrik Brueckner <brueckner@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Thomas Richter <tmricht@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Hendrik Brueckner <brueckner@xxxxxxxxxxxxxxxxxx>
---
tools/perf/util/evsel.c | 7 +++----
1 files changed, 3 insertions(+), 4 deletions(-)
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index ac59710..9266908 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -264,15 +264,14 @@ struct perf_evsel *perf_evsel__new_cycles(void)
event_attr_init(&attr);
- perf_event_attr__set_max_precise_ip(&attr);
-
evsel = perf_evsel__new(&attr);
if (evsel == NULL)
goto out;
+ evsel->precise_max = 1;
+
/* use asprintf() because free(evsel) assumes name is allocated */
- if (asprintf(&evsel->name, "cycles%.*s",
- attr.precise_ip ? attr.precise_ip + 1 : 0, ":ppp") < 0)
+ if (asprintf(&evsel->name, "cycles:P") < 0)
goto error_free;
out:
return evsel;
--
2.9.3
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