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SubjectRe: Unable to use tools/perf sched and timechart correctly


Török Edwin wrote:
> Hi,
>
> I installed 2.6.32 and tried its tools/perf.
> I noticed two problems so far, please tell me if I am doing anything
> wrong here:
>
> 1. 'perf sched replay' segfaults on any recorded workload
> I tested like this:
> $ sudo ./perf sched record
> ^C[ perf record: Woken up 1 times to write data ]
> [ perf record: Captured and wrote 0.295 MB perf.data (~12869 samples) ]
> $ sudo perf sched replay
> run measurement overhead: 1258 nsecs
> sleep measurement overhead: 55232 nsecs
> the run test took 999778 nsecs
> the sleep test took 1055791 nsecs
> nr_run_events: 182
> nr_sleep_events: 209
> nr_wakeup_events: 103
> target-less wakeups: 12
> [...]
> task 25 ( icedove-bin: 8757), nr_events: 3
> task 26 ( events/0: 15), nr_events: 3
> ------------------------------------------------------------
> Segmentation fault

You should enable "CONFIG_SCHED_DEBUG", because we use
"/proc/<pid>/sched" file to get the task's cpu usage.

Ingo, I think we do better show the reason about this error,
just like:

---
tools/perf/builtin-sched.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/tools/perf/builtin-sched.c b/tools/perf/builtin-sched.c
index 26b782f..f823631 100644
--- a/tools/perf/builtin-sched.c
+++ b/tools/perf/builtin-sched.c
@@ -427,7 +427,11 @@ static u64 get_cpu_usage_nsec_self(void)

sprintf(filename, "/proc/%d/sched", getpid());
file = fopen(filename, "r");
- BUG_ON(!file);
+ if (!file)
+ {
+ printf("You should compile your kernel with CONFIG_SCHED_DEBUG option\n");
+ BUG_ON(1);
+ }

while ((chars = getline(&line, &len, file)) != -1) {
ret = sscanf(line, "se.sum_exec_runtime : %ld.%06ld\n",
--
1.6.1.2
Thanks,
Xiao
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