perf tools: Look up thread names for system wide profiling
David Ahern [Thu, 22 Dec 2011 18:30:02 +0000 (11:30 -0700)]
This handles multithreaded processes with named threads when doing
system wide profiling: the comm for each thread is looked up allowing
them to be different from the thread group leader.

v2:
- fixed sizeof arg to perf_event__get_comm_tgid

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1324578603-12762-3-git-send-email-dsahern@gmail.com
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/event.c

index a578726..73ddaf0 100644 (file)
@@ -43,37 +43,27 @@ static struct perf_sample synth_sample = {
        .period    = 1,
 };
 
-static pid_t perf_event__synthesize_comm(struct perf_tool *tool,
-                                        union perf_event *event, pid_t pid,
-                                        int full, perf_event__handler_t process,
-                                        struct machine *machine)
+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;
-       DIR *tasks;
-       struct dirent dirent, *next;
-       pid_t tgid = 0;
+       pid_t tgid = -1;
 
        snprintf(filename, sizeof(filename), "/proc/%d/status", pid);
 
        fp = fopen(filename, "r");
        if (fp == NULL) {
-out_race:
-               /*
-                * We raced with a task exiting - just return:
-                */
                pr_debug("couldn't open %s\n", filename);
                return 0;
        }
 
-       memset(&event->comm, 0, sizeof(event->comm));
-
-       while (!event->comm.comm[0] || !event->comm.pid) {
+       while (!comm[0] || (tgid < 0)) {
                if (fgets(bf, sizeof(bf), fp) == NULL) {
-                       pr_warning("couldn't get COMM and pgid, malformed %s\n", filename);
-                       goto out;
+                       pr_warning("couldn't get COMM and pgid, malformed %s\n",
+                                  filename);
+                       break;
                }
 
                if (memcmp(bf, "Name:", 5) == 0) {
@@ -81,16 +71,46 @@ out_race:
                        while (*name && isspace(*name))
                                ++name;
                        size = strlen(name) - 1;
-                       memcpy(event->comm.comm, name, size++);
+                       if (size >= len)
+                               size = len - 1;
+                       memcpy(comm, name, size);
+
                } else if (memcmp(bf, "Tgid:", 5) == 0) {
                        char *tgids = bf + 5;
                        while (*tgids && isspace(*tgids))
                                ++tgids;
-                       tgid = event->comm.pid = atoi(tgids);
+                       tgid = atoi(tgids);
                }
        }
 
+       fclose(fp);
+
+       return tgid;
+}
+
+static pid_t perf_event__synthesize_comm(struct perf_tool *tool,
+                                        union perf_event *event, pid_t pid,
+                                        int full,
+                                        perf_event__handler_t process,
+                                        struct machine *machine)
+{
+       char filename[PATH_MAX];
+       size_t size;
+       DIR *tasks;
+       struct dirent dirent, *next;
+       pid_t tgid;
+
+       memset(&event->comm, 0, sizeof(event->comm));
+
+       tgid = perf_event__get_comm_tgid(pid, event->comm.comm,
+                                        sizeof(event->comm.comm));
+       if (tgid < 0)
+               goto out;
+
+       event->comm.pid = tgid;
        event->comm.header.type = PERF_RECORD_COMM;
+
+       size = strlen(event->comm.comm) + 1;
        size = ALIGN(size, sizeof(u64));
        memset(event->comm.comm + size, 0, machine->id_hdr_size);
        event->comm.header.size = (sizeof(event->comm) -
@@ -106,8 +126,10 @@ out_race:
        snprintf(filename, sizeof(filename), "/proc/%d/task", pid);
 
        tasks = opendir(filename);
-       if (tasks == NULL)
-               goto out_race;
+       if (tasks == NULL) {
+               pr_debug("couldn't open %s\n", filename);
+               return 0;
+       }
 
        while (!readdir_r(tasks, &dirent, &next) && next) {
                char *end;
@@ -115,6 +137,17 @@ out_race:
                if (*end)
                        continue;
 
+               /* already have tgid; jut want to update the comm */
+               (void) perf_event__get_comm_tgid(pid, event->comm.comm,
+                                        sizeof(event->comm.comm));
+
+               size = strlen(event->comm.comm) + 1;
+               size = ALIGN(size, sizeof(u64));
+               memset(event->comm.comm + size, 0, machine->id_hdr_size);
+               event->comm.header.size = (sizeof(event->comm) -
+                                         (sizeof(event->comm.comm) - size) +
+                                         machine->id_hdr_size);
+
                event->comm.tid = pid;
 
                process(tool, event, &synth_sample, machine);
@@ -122,8 +155,6 @@ out_race:
 
        closedir(tasks);
 out:
-       fclose(fp);
-
        return tgid;
 }