[Toybox] Interpreting top -H -O CPU output

[enh]

On Wed, Feb 6, 2019 at 2:34 PM Rob Landley <rob at landley.net> wrote:
>
> On 2/6/19 12:56 PM, Dmitry Shmidt wrote:
> > Hi Rob,
> >
> > I am using your top tool implementation for Android from
> > toybox project.
> > I am wondering if in the mode where it shows cpu usage
> > per thread, the total usage per task (process) is included in initial
> > ("main") thread?
>
> I don't really use threads much, Elliott provided most of the use cases for that.
>
> > For example: com.google.android.youtube.tv
> > <http://com.google.android.youtube.tv> shows 153% usage
> > for main thread and some more for other threads, like MainWebView - 31%.
> > Is this 31% included in 153% report or not?
>
> It should never report more than 100%, so it sounds like it is combining CPU
> usage from threads into the parent, yes.
>
> Hmmm... Top -H isn't showing TID by default,

yeah, that seemed a bit weird to me, but it matches what the
traditional implementation did. (though threads aren't as common on
the desktop.)

interestingly, i notice that our numbers don't add up. on the desktop,
total == running + sleeping, but our sleeping count is a lot lower
than it should be. (the desktop also says "Tasks:" or "Threads:"
depending on whether you supplied -H, and we don't.)

we also don't do a good job of sizing the PID field on machines with a
large pid_max. this fixes both of those minor issues, but between the
removal of the `const` on the array and the floating point math i
assume you'll want to do this differently :-)

diff --git a/toys/posix/ps.c b/toys/posix/ps.c
index 079bdbd6..50f52b41 100644
--- a/toys/posix/ps.c
+++ b/toys/posix/ps.c
@@ -314,9 +314,9 @@ struct procpid {
 struct typography {
   char *name, *help;
   signed char width, slot;
-} static const typos[] = TAGGED_ARRAY(PS,
+} static /*const*/ typos[] = TAGGED_ARRAY(PS,
   // Numbers. (What's in slot[] is what's displayed, sorted numerically.)
-  {"PID", "Process ID", 5, SLOT_pid},
+  {"PID", "Process ID", 2, SLOT_pid},
   {"PPID", "Parent Process ID", 5, SLOT_ppid},
   {"PRI", "Priority (dynamic 0 to 139)", 3, SLOT_priority},
   {"NI", "Niceness (static 19 to -20)", 3, SLOT_nice},
@@ -1262,6 +1262,16 @@ static void default_ko(char *s, void *fields, char *err,
struct arg_list *arg)
   if (x) help_help();
 }

+static void init_pid_width(void)
+{
+  FILE *fp = xfopen("/proc/sys/kernel/pid_max", "re");
+  int pid_max;
+
+  fscanf(fp, "%d", &pid_max);
+  fclose(fp);
+  typos[0].width = ceil(log10(pid_max));
+}
+
 void ps_main(void)
 {
   char **arg;
@@ -1270,6 +1280,7 @@ void ps_main(void)
   int i;

   TT.ticks = sysconf(_SC_CLK_TCK); // units for starttime/uptime
+  init_pid_width();

   if (-1 != (i = tty_fd())) {
     struct stat st;
@@ -1546,8 +1557,9 @@ static void top_common(
           for (i = 0; i<mix.count; i++)
             run[1+stridx("RSTZ", *string_field(mix.tb[i], &field))]++;
           sprintf(toybuf,
-            "Tasks: %d total,%4ld running,%4ld sleeping,%4ld stopped,"
-            "%4ld zombie", mix.count, run[1], run[2], run[3], run[4]);
+            "%ss: %d total, %3ld running, %3ld sleeping, %3ld stopped, "
+            "%3ld zombie", FLAG(H)?"Thread":"Task", mix.count,
+            run[1], run[2], run[3], run[4]);
           lines = header_line(lines, 0);

           if (readfile("/proc/meminfo", toybuf, sizeof(toybuf))) {
@@ -1697,6 +1709,7 @@ static void top_setup(char *defo, char *defk)
 {
   TT.ticks = sysconf(_SC_CLK_TCK); // units for starttime/uptime
   TT.tty = tty_fd() != -1;
+  init_pid_width();

   // Are we doing "batch" output or interactive?
   if (FLAG(b)) TT.width = TT.height = 99999;


> and top -H -O TID is never showing
> more than one instance of the same PID... until I sort by TID, and then I get a
> bunch of chrome threads under the same PID, each with 1.5% of the CPU. So yeah,
> CPU usage is per process here, not per thread.
>
> I'm trying to cut a release, but let me add that to the todo list for next
> release. (I should try to come up with a better test case because y system's way
> too loaded normally...)
>
> Rob
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