On Mon, Mar 30, 2015 at 02:35:57PM -0600, David Ahern wrote:
> 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.
Seeing Jiri is happy now. :-)
Acked-by: Don Zickus <dzic...@redhat.com>
>
> 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 the isspace checks on tgid string
>
> 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;
> }
> --
> 2.2.1
>
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