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perf evsel: Probe for precise_ip with simple attr 

Currently we probe for precise_ip with user specified perf_event_attr,
which might fail because of unsupported kernel features, which would get
disabled during the open time anyway.

Switching the probe to take place on simple hw cycles, so the following
record sets proper precise_ip:

  # perf record -e cycles:P ls
  # perf evlist -v
  cycles:P: size: 112, ... precise_ip: 3, ...

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jonas Rabenstein <jonas.rabenstein@studium.uni-erlangen.de>
Cc: Nageswara R Sastry <nasastry@in.ibm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@linux.ibm.com>
Link: http://lkml.kernel.org/r/20190305152536.21035-7-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Jiri Olsa 2019-03-05 16:25:34 +01:00 committed by Arnaldo Carvalho de Melo
parent 90a86bde97
commit 5b61adb165
2 changed files with 20 additions and 13 deletions
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25
tools/perf/util/evlist.c
View File

@ -230,18 +230,33 @@ void perf_evlist__set_leader(struct perf_evlist *evlist)
}
}
void perf_event_attr__set_max_precise_ip(struct perf_event_attr *attr)
void perf_event_attr__set_max_precise_ip(struct perf_event_attr *pattr)
{
attr->precise_ip = 3;
struct perf_event_attr attr = {
.type = PERF_TYPE_HARDWARE,
.config = PERF_COUNT_HW_CPU_CYCLES,
.exclude_kernel = 1,
.precise_ip = 3,
};
while (attr->precise_ip != 0) {
int fd = sys_perf_event_open(attr, 0, -1, -1, 0);
event_attr_init(&attr);
/*
* Unnamed union member, not supported as struct member named
* initializer in older compilers such as gcc 4.4.7
*/
attr.sample_period = 1;
while (attr.precise_ip != 0) {
int fd = sys_perf_event_open(&attr, 0, -1, -1, 0);
if (fd != -1) {
close(fd);
break;
}
--attr->precise_ip;
--attr.precise_ip;
}
pattr->precise_ip = attr.precise_ip;
}
int __perf_evlist__add_default(struct perf_evlist *evlist, bool precise)

8
tools/perf/util/evsel.c
View File

@ -294,20 +294,12 @@ struct perf_evsel *perf_evsel__new_cycles(bool precise)
if (!precise)
goto new_event;
/*
* Unnamed union member, not supported as struct member named
* initializer in older compilers such as gcc 4.4.7
*
* Just for probing the precise_ip:
*/
attr.sample_period = 1;
perf_event_attr__set_max_precise_ip(&attr);
/*
* Now let the usual logic to set up the perf_event_attr defaults
* to kick in when we return and before perf_evsel__open() is called.
*/
attr.sample_period = 0;
new_event:
evsel = perf_evsel__new(&attr);
if (evsel == NULL)