tjh.dev / kernel
Linux kernel mirror (for testing) git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel os linux
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perf script: Display negative tid in non-sample events

The kernel can release tasks while they are still running. This can
result in a task having no tid, in which case perf records a tid of -1.
Improve the perf script output in that case.

Example:

Before:

# cat ./autoreap.c

#include <sys/types.h>
#include <unistd.h>
#include <sys/wait.h>
#include <signal.h>

struct sigaction act = {
.sa_handler = SIG_IGN,
};

int main()
{
pid_t child;
int status = 0;

sigaction(SIGCHLD, &act, NULL);
child = fork();
if (child == 0)
return 123;
wait(&status);
return 0;
}

# gcc -o autoreap autoreap.c
# ./perf record -a -e dummy --switch-events ./autoreap
[ perf record: Woken up 1 times to write data ]
[ perf record: Captured and wrote 0.948 MB perf.data ]
# ./perf script --show-task-events --show-switch-events | grep -C2 'autoreap\|4294967295\|-1'
swapper 0 [004] 18462.673613: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 25189/25189
perf 25189 [004] 18462.673614: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0
autoreap 25189 [004] 18462.673800: PERF_RECORD_COMM exec: autoreap:25189/25189
autoreap 25189 [004] 18462.674042: PERF_RECORD_FORK(25191:25191):(25189:25189)
autoreap 25189 [004] 18462.674050: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0
swapper 0 [004] 18462.674051: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 25189/25189
swapper 0 [005] 18462.674083: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 25191/25191
autoreap 25191 [005] 18462.674084: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0
swapper 0 [003] 18462.674121: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 11/11
rcu_preempt 11 [003] 18462.674121: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0
rcu_preempt 11 [003] 18462.674124: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0
swapper 0 [003] 18462.674124: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 11/11
autoreap 25191 [005] 18462.674138: PERF_RECORD_EXIT(25191:25191):(25189:25189)
PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0
swapper 0 [005] 18462.674149: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 4294967295/4294967295
swapper 0 [004] 18462.674182: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 25189/25189
autoreap 25189 [004] 18462.674183: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0
autoreap 25189 [004] 18462.674218: PERF_RECORD_EXIT(25189:25189):(25188:25188)
autoreap 25189 [004] 18462.674225: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0
swapper 0 [004] 18462.674226: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 25189/25189
swapper 0 [007] 18462.674257: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 25188/25188

After:

# ./perf script --show-task-events --show-switch-events | grep -C2 'autoreap\|4294967295\|-1'
swapper 0 [004] 18462.673613: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 25189/25189
perf 25189 [004] 18462.673614: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0
autoreap 25189 [004] 18462.673800: PERF_RECORD_COMM exec: autoreap:25189/25189
autoreap 25189 [004] 18462.674042: PERF_RECORD_FORK(25191:25191):(25189:25189)
autoreap 25189 [004] 18462.674050: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0
swapper 0 [004] 18462.674051: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 25189/25189
swapper 0 [005] 18462.674083: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 25191/25191
autoreap 25191 [005] 18462.674084: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0
swapper 0 [003] 18462.674121: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 11/11
rcu_preempt 11 [003] 18462.674121: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0
rcu_preempt 11 [003] 18462.674124: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0
swapper 0 [003] 18462.674124: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 11/11
autoreap 25191 [005] 18462.674138: PERF_RECORD_EXIT(25191:25191):(25189:25189)
:-1 -1 [005] 18462.674149: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0
swapper 0 [005] 18462.674149: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: -1/-1
swapper 0 [004] 18462.674182: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 25189/25189
autoreap 25189 [004] 18462.674183: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 0/0
autoreap 25189 [004] 18462.674218: PERF_RECORD_EXIT(25189:25189):(25188:25188)
autoreap 25189 [004] 18462.674225: PERF_RECORD_SWITCH_CPU_WIDE OUT next pid/tid: 0/0
swapper 0 [004] 18462.674226: PERF_RECORD_SWITCH_CPU_WIDE IN prev pid/tid: 25189/25189
swapper 0 [007] 18462.674257: PERF_RECORD_SWITCH_CPU_WIDE OUT preempt next pid/tid: 25188/25188

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Yu-cheng Yu <yu-cheng.yu@intel.com>
Link: http://lore.kernel.org/lkml/20200909084923.9096-2-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

authored by

Adrian Hunter and committed by
Arnaldo Carvalho de Melo fc18380f 99f63817

+7 -5
+6 -4
tools/perf/builtin-script.c
··· 702 702 char tstr[128]; 703 703 704 704 if (PRINT_FIELD(COMM)) { 705 + const char *comm = thread ? thread__comm_str(thread) : ":-1"; 706 + 705 707 if (latency_format) 706 - printed += fprintf(fp, "%8.8s ", thread__comm_str(thread)); 708 + printed += fprintf(fp, "%8.8s ", comm); 707 709 else if (PRINT_FIELD(IP) && evsel__has_callchain(evsel) && symbol_conf.use_callchain) 708 - printed += fprintf(fp, "%s ", thread__comm_str(thread)); 710 + printed += fprintf(fp, "%s ", comm); 709 711 else 710 - printed += fprintf(fp, "%16s ", thread__comm_str(thread)); 712 + printed += fprintf(fp, "%16s ", comm); 711 713 } 712 714 713 715 if (PRINT_FIELD(PID) && PRINT_FIELD(TID)) ··· 2240 2238 if (tid != -1) 2241 2239 thread = machine__findnew_thread(machine, pid, tid); 2242 2240 2243 - if (thread && evsel) { 2241 + if (evsel) { 2244 2242 perf_sample__fprintf_start(script, sample, thread, evsel, 2245 2243 event->header.type, stdout); 2246 2244 }
+1 -1
tools/perf/util/event.c
··· 398 398 if (event->header.type == PERF_RECORD_SWITCH) 399 399 return fprintf(fp, " %s\n", in_out); 400 400 401 - return fprintf(fp, " %s %s pid/tid: %5u/%-5u\n", 401 + return fprintf(fp, " %s %s pid/tid: %5d/%-5d\n", 402 402 in_out, out ? "next" : "prev", 403 403 event->context_switch.next_prev_pid, 404 404 event->context_switch.next_prev_tid);