On Wed, Mar 25, 2015 at 10:51:10AM -0600, David Ahern wrote: > 363b785f38 added synthesized fork events and set a thread's parent id > to itself. Since we are already processing /proc/<pid>/status the ppid > can be determined properly. Make it so. > > Performance impact measured on a sparc based T5-8 (1024 CPUs): > $ ps -efL | wc -l > 20185 > > Current code: > $ time perf record -o perf-no-ppid.data -e cpu-clock -F 1000 -a -v -BN -- > usleep 1 > mmap size 532480B > [ perf record: Woken up 0 times to write data ] > failed to write feature 9 > [ perf record: Captured and wrote 0.000 MB perf-no-ppid.data ] > > real 0m26.144s > user 0m0.452s > sys 0m25.564s > > With PPID patch: > $ time ./perf_ppid record -o perf-ppid.data -e cpu-clock -F 1000 -a -v -BN -- > usleep 1 > mmap size 532480B > [ perf record: Woken up 0 times to write data ] > failed to write feature 9 > [ perf record: Captured and wrote 0.000 MB perf-ppid.data ] > > real 0m25.743s > user 0m0.268s > sys 0m25.368s > > Signed-off-by: David Ahern <dsah...@gmail.com> > Cc: Don Zickus <dzic...@redhat.com> > Cc: Joe Mario <jma...@redhat.com> > Cc: Jiri Olsa <jo...@redhat.com> > --- > v2: > - removed loop in place of 1 read and processing a buffer
Hmm, I am not entirely sure this is correct. You made an optimization that hides the negative impact your patch does. I would prefer you split this patch into two pieces. One with the read loop optimization (which I think is great) and the second is your ppid change. I would then like to redo our test with the first patch applied and then both patches applied. I still think something is strange in the sense perf wasn't supposed to read the /proc filesystem again for threads. It was supposed to inherit the thread data from the parent (the original intent and big speed up of my patch). I believe your patch breaks that and goes back to reading the /proc filesystem again. :-( Though I haven't had a chance to figure out why. Cheers, Don > > tools/perf/util/event.c | 178 > ++++++++++++++++++++++++++++++------------------ > 1 file changed, 110 insertions(+), 68 deletions(-) > > diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c > index d5efa5092ce6..e98cbba56033 100644 > --- a/tools/perf/util/event.c > +++ b/tools/perf/util/event.c > @@ -49,70 +49,115 @@ static struct perf_sample synth_sample = { > .period = 1, > }; > > -static pid_t perf_event__get_comm_tgid(pid_t pid, char *comm, size_t len) > +/* > + * Assumes that the first 4095 bytes of /proc/pid/stat contains > + * the comm, tgid and ppid. > + */ > +static int perf_event__get_comm_ids(pid_t pid, char *comm, size_t len, > + pid_t *tgid, pid_t *ppid) > { > char filename[PATH_MAX]; > - char bf[BUFSIZ]; > - FILE *fp; > - size_t size = 0; > - pid_t tgid = -1; > + char bf[4096]; > + int fd; > + size_t size = 0, n; > + char *nl, *name, *tgids, *ppids; > + > + *tgid = -1; > + *ppid = -1; > > 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; > + return -1; > } > > - 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; > - } > - > - 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'; > - > - } else if (memcmp(bf, "Tgid:", 5) == 0) { > - char *tgids = bf + 5; > - while (*tgids && isspace(*tgids)) > - ++tgids; > - tgid = atoi(tgids); > - } > + n = read(fd, bf, sizeof(bf) - 1); > + close(fd); > + if (n <= 0) { > + pr_warning("Couldn't get COMM, tigd and ppid for pid %d\n", > + pid); > + return -1; > } > + bf[n] = '\0'; > > - fclose(fp); > + name = strstr(bf, "Name:"); > + tgids = strstr(bf, "Tgid:"); > + ppids = strstr(bf, "PPid:"); > + > + 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); > + > + if (tgids) { > + tgids += 5; /* strlen("Tgid:") */ > + while (*tgids && isspace(*tgids)) > + ++tgids; > + > + nl = strchr(tgids, '\n'); > + if (nl) > + *nl = '\0'; > + > + *tgid = atoi(tgids); > + > + } else > + pr_debug("Tgid: string not found for pid %d\n", pid); > + > + if (ppids) { > + ppids += 5; /* strlen("PPid:") */ > + > + while (*ppids && isspace(*ppids)) > + ++ppids; > + > + nl = strchr(ppids, '\n'); > + if (nl) > + *nl = '\0'; > + > + *ppid = atoi(ppids); > + } else > + pr_debug("PPid: string not found for pid %d\n", pid); > > - return tgid; > + return 0; > } > > -static pid_t perf_event__prepare_comm(union perf_event *event, pid_t pid, > - struct machine *machine) > +static int perf_event__prepare_comm(union perf_event *event, pid_t pid, > + struct machine *machine, > + pid_t *tgid, pid_t *ppid) > { > size_t size; > - pid_t tgid; > + > + *ppid = -1; > > memset(&event->comm, 0, sizeof(event->comm)); > > - if (machine__is_host(machine)) > - tgid = perf_event__get_comm_tgid(pid, event->comm.comm, > - sizeof(event->comm.comm)); > - else > - tgid = machine->pid; > + if (machine__is_host(machine)) { > + if (perf_event__get_comm_ids(pid, event->comm.comm, > + sizeof(event->comm.comm), > + tgid, ppid) != 0) { > + return -1; > + } > + } else > + *tgid = machine->pid; > > - if (tgid < 0) > - goto out; > + if (*tgid < 0) > + return -1; > > - event->comm.pid = tgid; > + event->comm.pid = *tgid; > event->comm.header.type = PERF_RECORD_COMM; > > size = strlen(event->comm.comm) + 1; > @@ -122,36 +167,35 @@ static pid_t perf_event__prepare_comm(union perf_event > *event, pid_t pid, > (sizeof(event->comm.comm) - size) + > machine->id_hdr_size); > event->comm.tid = pid; > -out: > - return tgid; > + > + return 0; > } > > -static pid_t perf_event__synthesize_comm(struct perf_tool *tool, > - union perf_event *event, pid_t pid, > - perf_event__handler_t process, > - struct machine *machine) > +static int perf_event__synthesize_comm(struct perf_tool *tool, > + union perf_event *event, pid_t pid, > + perf_event__handler_t process, > + struct machine *machine, > + pid_t *tgid, pid_t *ppid) > { > - pid_t tgid = perf_event__prepare_comm(event, pid, machine); > - > - if (tgid == -1) > - goto out; > + if (perf_event__prepare_comm(event, pid, machine, tgid, ppid) != 0) > + return -1; > > if (process(tool, event, &synth_sample, machine) != 0) > return -1; > > -out: > - return tgid; > + return 0; > } > > static int perf_event__synthesize_fork(struct perf_tool *tool, > - union perf_event *event, pid_t pid, > - pid_t tgid, perf_event__handler_t > process, > + union perf_event *event, > + pid_t pid, pid_t tgid, pid_t ppid, > + perf_event__handler_t process, > struct machine *machine) > { > memset(&event->fork, 0, sizeof(event->fork) + machine->id_hdr_size); > > - event->fork.ppid = tgid; > - event->fork.ptid = tgid; > + event->fork.ppid = ppid; > + event->fork.ptid = ppid; > event->fork.pid = tgid; > event->fork.tid = pid; > event->fork.header.type = PERF_RECORD_FORK; > @@ -343,14 +387,12 @@ static int __event__synthesize_thread(union perf_event > *comm_event, > char filename[PATH_MAX]; > DIR *tasks; > struct dirent dirent, *next; > - pid_t tgid; > + pid_t tgid, ppid; > > /* special case: only send one comm event using passed in pid */ > if (!full) { > - tgid = perf_event__synthesize_comm(tool, comm_event, pid, > - process, machine); > - > - if (tgid == -1) > + if (perf_event__synthesize_comm(tool, comm_event, pid, > + process, machine, &tgid, &ppid) > != 0) > return -1; > > return perf_event__synthesize_mmap_events(tool, mmap_event, > pid, tgid, > @@ -378,12 +420,12 @@ static int __event__synthesize_thread(union perf_event > *comm_event, > if (*end) > continue; > > - tgid = perf_event__prepare_comm(comm_event, _pid, machine); > - if (tgid == -1) > + if (perf_event__prepare_comm(comm_event, _pid, machine, > + &tgid, &ppid) != 0) > return -1; > > if (perf_event__synthesize_fork(tool, fork_event, _pid, tgid, > - process, machine) < 0) > + ppid, process, machine) < 0) > return -1; > /* > * Send the prepared comm event > -- > 2.1.0 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/