Chris Adams writes:
> Once upon a time, Albert D. Cahalan <acahalan@cs.uml.edu> said:
>> BTW, let's start with: not only "ps" is affected.
>> Off the top of my head: netstat, fuser, top, pstree...
>
> netstat: already wraps around and loses formatting when PIDs are shown
> (so no changes)
Sure, but no need to make it worse.
> fuser: already has enough columns (because it uses "kernel" some places)
> (so no changes)
> top: two line change
Still this is screwing the common case for the truly unusual.
> pstree: PIDs are displayed in "()" after process name (not formatted
> columns) (so no changes)
>
> How many people actually _use_ PIDs on a regular basis? When I did our
> upgrade from Tru64 4.x to 5.x and got bigger PIDs, it took awhile before
> anyone else even noticed. Almost always when I'm doing something to
> processes, I'm scripting it, not typing numbers.
I'm not counting Aunt Tillie.
Anybody on a terminal without cut-and-paste will suffer.
>> I almost put 99999, but then I realized that that's silly.
>> For years Linux had a hard limit of about 4000 processes,
>> and not many people complained. It sure would be nice to
>> gain back a few of the columns lost to other stuff, so
>> that people could once again see command arguments.
>
> We're talking one or two more columns.
It's as many as 25 character-columns. Linus was using
0x3fffffff as a mask. There are 5 field-columns with
PID data in the "ps j" format.
> That's not going to magically
> make it possible to see the command arguments. If someone wants to see
> the arguments, they're going to have to use "w" anyway (also, "normal"
> ps with no arguments still has lots of space).
Huh? Try "ps -jf", which BTW has 4 PID columns. Also try "ps j".
I'm seeing arguments, and won't if PIDs get too wide.
>> The two real-word usage examples close at hand:
>>
>> a. My full GNOME desktop has 48 processes.
>>
>> b. The main UNIX shell server for CS students
>> at this university has 79 processes.
>> (Tru64, several hundred CS students, 2:25 am)
>
> My GNOME desktop has 72 processes, and I've only got Mozilla and a
> couple of xterms running right now.
Same as me, but I run Debian. Still, 72 is well below 9999.
> My Tru64 server, with only 9 users
> at 7:40 am, has 443 processes (during the business day we typically get
> a lot more processes - we'll have 50-75 users logged in, lots of POP
> checks running, and the usually at least once per day spam attack adding
> a couple of hundred extra sendmail processes - that's when we hit 1000+
> processes).
While I think this would fit under 9999, you're welcome
to adjust your system for any limit you like. I just don't
think the default should cater to systems that are both
rare and likely to have a real paid admin. It's your job to
increase the limit if you feel a need for more PID space.
>> The problem is screen space, pure and simple. If the
>> default limit goes to over 1 billion, then "ps" output
>> must wrap lines. There is no alternative, unless you
>> think "System going down to reset PID numbers!" is OK.
>
> Adding just one column (and going to 19 bits) allows 16
> times as many PIDs (or a sparse space 16 times as large).
Yes, and it trashes many common formats.
>>> $ ps -lf | head -2
>>> F S UID PID PPID %CPU PRI NI RSS WCHAN STARTED TIME COMMAND
>>> 80c08001 I 200 272363 301021 0.0 44 0 520K wait 20:47:46 0:00.09 -bash (bash)
>>
>> Eeew. That's broken; it won't display right on a normal
>> 80x24 terminal. Linux "ps -lf" will just barely fit.
>
> Why does every possible output format of ps have to fit each process on
> one line? How often are these output formats used by normal people?
How often are thousands of PIDs used by normal people?
>>> $ ps j | head -2
>>> USER PID PPID PGID SESS JOBC S TTY TIME COMMAND
>>> cmadams 272363 301021 272363 272363 0 I pts/1 0:00.09 -bash (bash)
>
> Note: one reason this one wrapped (instead of chopping the command) is
> that Tru64 ps automatically displays everything (like lots of "w"
> options) when output is not a TTY.
It's either that or assume 80, unless you have a way to
get info from the controlling tty. I haven't looked into
that yet.
>> It's not just "ps", and I'm not saying you couldn't
>> adjust your system for a higher limit. I do think that
>> the out-of-box default shouldn't screw up formatting.
>> If you need to go past 9999, then you'll want to tweak
>> a few other settings as well. Low process counts are
>> the common case, and shouldn't be hurt by the fact that
>> a few people wish to run a billion processes.
>
> I'm not talking about a billion processes.
That's what Linus was testing with.
> Also, are you going to make
> all those other programs (well, "top" is the only one named above that
> has to be changed) handle variable width PIDs now too? That argument
> cuts both ways.
Perhaps. You, with the odd case, can do without those programs.
> I think setting things based on formatting of some modes of a couple of
> programs that not that many users actually use is not the right way to
> go. We don't limit usernames to 8 characters anymore just because "ls"
> truncates the name (not a kernel issue but the same concept). If a
> larger PID space works better for PID allocation, then go with a larger
> PID space.
Arrrgh! That's a bug in ls, and yes you should limit usernames.
Think about:
Albert_Roberts
Albert_Robertson
Albert_Robbens
I think this is a much more popular problem than PID issues.
Lots of people with an NT background don't see why a long
username might cause problems. (names may be assigned by
corporate policy, and Linux admins must adapt) Maybe I could
do something about this if the default PID limit was 9999.
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This archive was generated by hypermail 2b29 : Thu Aug 15 2002 - 22:00:19 EST