perf tools: Refactor comm/tgid lookup
Rather than parsing /proc/pid/status file one line at a time, read it
into a buffer in one shot and search for all strings in one pass.
tgid conversion also simplified -- removing the isspace walk. As noted
by Arnaldo those are not needed for atoi == strtol calls.
Signed-off-by: David Ahern <dsahern@gmail.com>
Acked-by: Don Zickus <dzickus@redhat.com>
Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Joe Mario <jmario@redhat.com>
Link: http://lkml.kernel.org/r/1427747758-18510-1-git-send-email-dsahern@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c
index d5efa50..023dd35 100644
--- a/tools/perf/util/event.c
+++ b/tools/perf/util/event.c
@@ -49,48 +49,64 @@
.period = 1,
};
+/*
+ * Assumes that the first 4095 bytes of /proc/pid/stat contains
+ * the comm and tgid.
+ */
static pid_t perf_event__get_comm_tgid(pid_t pid, char *comm, size_t len)
{
char filename[PATH_MAX];
- char bf[BUFSIZ];
- FILE *fp;
- size_t size = 0;
+ char bf[4096];
+ int fd;
+ size_t size = 0, n;
pid_t tgid = -1;
+ char *nl, *name, *tgids;
snprintf(filename, sizeof(filename), "/proc/%d/status", pid);
- fp = fopen(filename, "r");
- if (fp == NULL) {
+ fd = open(filename, O_RDONLY);
+ if (fd < 0) {
pr_debug("couldn't open %s\n", filename);
return 0;
}
- while (!comm[0] || (tgid < 0)) {
- if (fgets(bf, sizeof(bf), fp) == NULL) {
- pr_warning("couldn't get COMM and pgid, malformed %s\n",
- filename);
- break;
- }
+ n = read(fd, bf, sizeof(bf) - 1);
+ close(fd);
+ if (n <= 0) {
+ pr_warning("Couldn't get COMM and tgid for pid %d\n",
+ pid);
+ return -1;
+ }
+ bf[n] = '\0';
- if (memcmp(bf, "Name:", 5) == 0) {
- char *name = bf + 5;
- while (*name && isspace(*name))
- ++name;
- size = strlen(name) - 1;
- if (size >= len)
- size = len - 1;
- memcpy(comm, name, size);
- comm[size] = '\0';
+ name = strstr(bf, "Name:");
+ tgids = strstr(bf, "Tgid:");
- } else if (memcmp(bf, "Tgid:", 5) == 0) {
- char *tgids = bf + 5;
- while (*tgids && isspace(*tgids))
- ++tgids;
- tgid = atoi(tgids);
- }
+ if (name) {
+ name += 5; /* strlen("Name:") */
+
+ while (*name && isspace(*name))
+ ++name;
+
+ nl = strchr(name, '\n');
+ if (nl)
+ *nl = '\0';
+
+ size = strlen(name);
+ if (size >= len)
+ size = len - 1;
+ memcpy(comm, name, size);
+ comm[size] = '\0';
+ } else {
+ pr_debug("Name: string not found for pid %d\n", pid);
}
- fclose(fp);
+ if (tgids) {
+ tgids += 5; /* strlen("Tgid:") */
+ tgid = atoi(tgids);
+ } else {
+ pr_debug("Tgid: string not found for pid %d\n", pid);
+ }
return tgid;
}