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perf tools: Use scandir() to replace readdir()

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In perf_event__synthesize_threads() perf goes through all proc files
serially by readdir.

scandir() does a snapshoot of /proc, which is multithreading friendly.

It's possible that some threads which are added during event synthesize.
But the number of lost threads should be small.  They should not impact
the final analysis.

Signed-off-by: Kan Liang <kan.liang@intel.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Lukasz Odzioba <lukasz.odzioba@intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1504806954-150842-3-git-send-email-kan.liang@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
This commit is contained in:
Kan Liang 2017-09-07 10:55:46 -07:00 committed by Arnaldo Carvalho de Melo
parent 8233822f40
commit ecdad24d7a
1 changed files with 25 additions and 20 deletions
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29
tools/perf/util/event.c
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@ -683,12 +683,14 @@ int perf_event__synthesize_threads(struct perf_tool *tool,
bool mmap_data,
unsigned int proc_map_timeout)
{
DIR *proc;
char proc_path[PATH_MAX];
struct dirent *dirent;
union perf_event *comm_event, *mmap_event, *fork_event;
union perf_event *namespaces_event;
char proc_path[PATH_MAX];
struct dirent **dirent;
int err = -1;
char *end;
pid_t pid;
int n, i;
if (machine__is_default_guest(machine))
return 0;
@ -712,17 +714,18 @@ int perf_event__synthesize_threads(struct perf_tool *tool,
goto out_free_fork;
snprintf(proc_path, sizeof(proc_path), "%s/proc", machine->root_dir);
proc = opendir(proc_path);
n = scandir(proc_path, &dirent, 0, alphasort);
if (proc == NULL)
if (n < 0)
goto out_free_namespaces;
while ((dirent = readdir(proc)) != NULL) {
char *end;
pid_t pid = strtol(dirent->d_name, &end, 10);
if (*end) /* only interested in proper numerical dirents */
for (i = 0; i < n; i++) {
if (!isdigit(dirent[i]->d_name[0]))
continue;
pid = (pid_t)strtol(dirent[i]->d_name, &end, 10);
/* only interested in proper numerical dirents */
if (!*end) {
/*
* We may race with exiting thread, so don't stop just because
* one thread couldn't be synthesized.
@ -732,9 +735,11 @@ int perf_event__synthesize_threads(struct perf_tool *tool,
tool, machine, mmap_data,
proc_map_timeout);
}
free(dirent[i]);
}
free(dirent);
err = 0;
closedir(proc);
out_free_namespaces:
free(namespaces_event);
out_free_fork: