[Toybox] ps debugging (notes to self)

[Rob Landley]

To do a manual data dump with slot labels, decimal, and hex values:

cat /proc/$$/stat | xargs -n 1 | \
  (X=0; while read i; do \
   echo -n "[$X:$i:$(printf %x $i)] "; X=$(($X+1)); done); \
   echo && ps -o pid,rss

Use $$ as a stable (per-window) process whose values don't generally
change between invocations. (It's the shell you're running, stays
persistent where /proc/self doesn't. /proc/$PPID is the shell's parent,
I.E. an xterm, which is this crappy horrible thing where /proc/self/maps
goes on for PAGES on ubuntu.)

The slot[] values are in table 1-4 of the kernel's
Documentation/filesystems/proc.txt but the slot[] array entries after
the first are off by 2 because "tcomm" and "state" aren't numerical
values and are stored in variables outside the table. So the above data
dump has rss at 23 when it's slot[21].

Here's a slot[] labeled version of the table:

Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
..............................................................................
 Field          Content
0  pid           process id
  tcomm         filename of the executable
  state         state (R is running, S is sleeping, D is sleeping in an
                uninterruptible wait, Z is zombie, T is traced/stopped)
1  ppid          process id of the parent process
2  pgrp          pgrp of the process
3  sid           session id
4  tty_nr        tty the process uses
5  tty_pgrp      pgrp of the tty
6  flags         task flags
7  min_flt       number of minor faults
8  cmin_flt      number of minor faults with child's
9  maj_flt       number of major faults
10 cmaj_flt      number of major faults with child's
11 utime         user mode jiffies
12 stime         kernel mode jiffies
13 cutime        user mode jiffies with child's
14 cstime        kernel mode jiffies with child's
15 priority      priority level
16 nice          nice level
17 num_threads   number of threads
18 it_real_value        (obsolete, always 0)
19 start_time    time the process started after system boot
20 vsize         virtual memory size
21 rss           resident set memory size
22 rsslim        current limit in bytes on the rss
23 start_code    address above which program text can run
24 end_code      address below which program text can run
25 start_stack   address of the start of the main process stack
26 esp           current value of ESP
27 eip           current value of EIP
28 pending       bitmap of pending signals
29 blocked       bitmap of blocked signals
30 sigign        bitmap of ignored signals
31 sigcatch      bitmap of caught signals
32 wchan         address where process went to sleep
33 0             (place holder)
34 0             (place holder)
35 exit_signal   signal to send to parent thread on exit
36 task_cpu      which CPU the task is scheduled on
37 rt_priority   realtime priority
38 policy        scheduling policy (man sched_setscheduler)
39 blkio_ticks   time spent waiting for block IO
40 gtime         guest time of the task in jiffies
41 cgtime        guest time of the task children in jiffies
42 start_data    address above which program data+bss is placed
43 end_data      address below which program data+bss is placed
44 start_brk     address above which program heap can be brk() expanded
45 arg_start     address above which program command line is placed
46 arg_end       address below which program command line is placed
47 env_start     address above which program environment is placed
48 env_end       address below which program environment is placed
49 exit_code     the thread's exit_code in the form reported by waitpid

Unsolved problem: how the HECK do you test things like "rss" when
they'll vary per platform even if you compile your own test.c file to
get a binary to run? Even in a known test image running under qemu, the
tests are inherently unportable. Easy to test by hand, very difficult to
automate unless you're providing your own synthetic /proc/1/stat data
with a --bind mount which is just... ew. I'm going to have to do that,
aren't I? Sigh...

I need to genericize the column alignment code ala "ls -l" and "vmstat".
I have no idea how to do that, but it comes up a lot and I keep having
to hand-code it each time...

Right, don't mind me. As I said, notes to self.

Rob

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