From 5aa0b030e8d29d6719c144818814b519cfcb105c Mon Sep 17 00:00:00 2001 From: David Ahern Date: Mon, 30 Mar 2015 14:35:57 -0600 Subject: [PATCH] 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 Acked-by: Don Zickus Acked-by: Jiri Olsa Cc: Joe Mario Link: http://lkml.kernel.org/r/1427747758-18510-1-git-send-email-dsahern@gmail.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/event.c | 72 +++++++++++++++++++++++++---------------- 1 file changed, 44 insertions(+), 28 deletions(-) diff --git a/tools/perf/util/event.c b/tools/perf/util/event.c index d5efa5092ce6..023dd3548a94 100644 --- a/tools/perf/util/event.c +++ b/tools/perf/util/event.c @@ -49,48 +49,64 @@ static struct perf_sample synth_sample = { .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'; - - } else if (memcmp(bf, "Tgid:", 5) == 0) { - char *tgids = bf + 5; - while (*tgids && isspace(*tgids)) - ++tgids; - tgid = atoi(tgids); - } + name = strstr(bf, "Name:"); + tgids = strstr(bf, "Tgid:"); + + 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; } -- 2.20.1