About PID...???!!!

About PID...???!!!

[Silambu Chelvan]

Hi All,

I have been using linux for quite some time. I wonder
how the PID is assigned by the kernel. Is there
anything like range of PID for each user? In my
machine I could see PIDs of 256, 389, 413 etc. Does
this mean that there are almost 413 processes running?

Please explain.....

with regards,
M. SilambuChelvan

__________________________________
Do you Yahoo!?
Yahoo! SiteBuilder - Free, easy-to-use web site design software
http://sitebuilder.yahoo.com
-
To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.linux-learn.org/faqs

Re: About PID...???!!!

[John T. Williams]

They are assigned linearly, however once a pid is used, it is never reused
until the machine reboots.

A pid of 413 means that when that process was fork()'ed there had been 412
other processes already created. But remember every time you type ls, you've
run a process.

413 isn't a large pid at all. My linux box which I very rarely reboot is at
PIDs that start at 20000

I'm surprised that any program you start after the boot process is as low as
412.



----- Original Message -----
From: "Silambu Chelvan" <silambu_mdu@yahoo.com>
To: <linux-newbie@vger.kernel.org>
Sent: Wednesday, September 10, 2003 10:23 AM
Subject: About PID...???!!!


> Hi All,
>
> I have been using linux for quite some time. I wonder
> how the PID is assigned by the kernel. Is there
> anything like range of PID for each user? In my
> machine I could see PIDs of 256, 389, 413 etc. Does
> this mean that there are almost 413 processes running?
>
> Please explain.....
>
> with regards,
> M. SilambuChelvan
>
> __________________________________
> Do you Yahoo!?
> Yahoo! SiteBuilder - Free, easy-to-use web site design software
> http://sitebuilder.yahoo.com
> -
> To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.linux-learn.org/faqs

-
To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.linux-learn.org/faqs

Re: About PID...???!!!

[Ray Olszewski]

At 11:21 AM 9/10/2003 -0400, John T. Williams wrote:
>They are assigned linearly, however once a pid is used, it is never reused
>until the machine reboots.

This is not quite correct. The pid assignment process wraps, I *think* at 
32767 (or maybe 65535). Next time around, the kernel skips over any pids 
that are still in use from the last round of assignment.

>A pid of 413 means that when that process was fork()'ed there had been 412
>other processes already created. But remember every time you type ls, you've
>run a process.
>
>413 isn't a large pid at all. My linux box which I very rarely reboot is at
>PIDs that start at 20000
>
>I'm surprised that any program you start after the boot process is as low as
>412.

Whether that is surprising or not depends on what he uses the host for and, 
naturally, on how recently it was rebooted. While my workstation is way up 
there (30180), my Linux-based router, which does not start new processes 
very much, is only at pid 828.

And, of course, there are persistent processes on any Linux host that go 
back to the boot/init process ... starting with init itself (always pid 1) 
and including long-lived daemons such as syslogd, klogd, and portmap; 
pseudo processes that are actually run in the kernel (mostly [k*] process 
names); and getty proceses listening on VTs that never get logins.



-
To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.linux-learn.org/faqs

Re: About PID...???!!!

[John T. Williams]

definitely higher then 2^16, I've got a process with the PID of 69917
I would guess MAX_INT which is 2^32 -1 = 4294967295


----- Original Message ----- 
From: "Ray Olszewski" <ray@comarre.com>
To: <linux-newbie@vger.kernel.org>
Sent: Wednesday, September 10, 2003 11:58 AM
Subject: Re: About PID...???!!!


> At 11:21 AM 9/10/2003 -0400, John T. Williams wrote:
> >They are assigned linearly, however once a pid is used, it is never
reused
> >until the machine reboots.
>
> This is not quite correct. The pid assignment process wraps, I *think* at
> 32767 (or maybe 65535). Next time around, the kernel skips over any pids
> that are still in use from the last round of assignment.
>
> >A pid of 413 means that when that process was fork()'ed there had been
412
> >other processes already created. But remember every time you type ls,
you've
> >run a process.
> >
> >413 isn't a large pid at all. My linux box which I very rarely reboot is
at
> >PIDs that start at 20000
> >
> >I'm surprised that any program you start after the boot process is as low
as
> >412.
>
> Whether that is surprising or not depends on what he uses the host for
and,
> naturally, on how recently it was rebooted. While my workstation is way up
> there (30180), my Linux-based router, which does not start new processes
> very much, is only at pid 828.
>
> And, of course, there are persistent processes on any Linux host that go
> back to the boot/init process ... starting with init itself (always pid 1)
> and including long-lived daemons such as syslogd, klogd, and portmap;
> pseudo processes that are actually run in the kernel (mostly [k*] process
> names); and getty proceses listening on VTs that never get logins.
>
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.linux-learn.org/faqs

-
To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.linux-learn.org/faqs

Re: About PID...???!!!

[John T. Williams]

definitely higher then 2^16, I've got a process with the PID of 69917
I would guess MAX_INT which is 2^32 -1 = 4294967295

----- Original Message ----- 
From: "Ray Olszewski" <ray@comarre.com>
To: <linux-newbie@vger.kernel.org>
Sent: Wednesday, September 10, 2003 11:58 AM
Subject: Re: About PID...???!!!


> At 11:21 AM 9/10/2003 -0400, John T. Williams wrote:
> >They are assigned linearly, however once a pid is used, it is never
reused
> >until the machine reboots.
>
> This is not quite correct. The pid assignment process wraps, I *think* at
> 32767 (or maybe 65535). Next time around, the kernel skips over any pids
> that are still in use from the last round of assignment.
>
> >A pid of 413 means that when that process was fork()'ed there had been
412
> >other processes already created. But remember every time you type ls,
you've
> >run a process.
> >
> >413 isn't a large pid at all. My linux box which I very rarely reboot is
at
> >PIDs that start at 20000
> >
> >I'm surprised that any program you start after the boot process is as low
as
> >412.
>
> Whether that is surprising or not depends on what he uses the host for
and,
> naturally, on how recently it was rebooted. While my workstation is way up
> there (30180), my Linux-based router, which does not start new processes
> very much, is only at pid 828.
>
> And, of course, there are persistent processes on any Linux host that go
> back to the boot/init process ... starting with init itself (always pid 1)
> and including long-lived daemons such as syslogd, klogd, and portmap;
> pseudo processes that are actually run in the kernel (mostly [k*] process
> names); and getty proceses listening on VTs that never get logins.
>
>
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.linux-learn.org/faqs

-
To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.linux-learn.org/faqs

Re: About PID...???!!!

[Ray Olszewski]

At 02:04 PM 9/10/2003 -0400, John T. Williams wrote:
>definitely higher then 2^16, I've got a process with the PID of 69917
>I would guess MAX_INT which is 2^32 -1 = 4294967295

Actually, as it turns out, the right answer is "it depends".

Checking my kernel source, I find that the kernel's fork() routine checks 
against PID_MAX before wrapping. This value is defined, at least for 
2.4.19, in <kernel_source_path>/include/linux/threads.h . My (Debian) 
kernel source has there

         #define PID_MAX 0x8000

which matches my observed wrapping at (or near) 32768 . You might see if 
your kernel source sets this value higher.

>----- Original Message -----
>From: "Ray Olszewski" <ray@comarre.com>
>To: <linux-newbie@vger.kernel.org>
>Sent: Wednesday, September 10, 2003 11:58 AM
>Subject: Re: About PID...???!!!
>
>
> > At 11:21 AM 9/10/2003 -0400, John T. Williams wrote:
> > >They are assigned linearly, however once a pid is used, it is never
>reused
> > >until the machine reboots.
> >
> > This is not quite correct. The pid assignment process wraps, I *think* at
> > 32767 (or maybe 65535). Next time around, the kernel skips over any pids
> > that are still in use from the last round of assignment.
[...]



-
To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.linux-learn.org/faqs

Re: About PID...???!!!

[John T. Williams]

Alright Alright, I concede it does loop, I should have used the word never.
I'll change it to rarely and be done with it, in any case I think Silambu
got his answer which briefly is:

No PID = 412 doesn't mean there are 412 process currently running on your
machine.
Read the man page for ps to learn how to identify processes that are
currently running.

----- Original Message ----- 
From: "John T. Williams" <jowillia@vt.edu>
To: <linux-newbie@vger.kernel.org>
Sent: Wednesday, September 10, 2003 2:04 PM
Subject: Re: About PID...???!!!


> definitely higher then 2^16, I've got a process with the PID of 69917
> I would guess MAX_INT which is 2^32 -1 = 4294967295
>
> ----- Original Message ----- 
> From: "Ray Olszewski" <ray@comarre.com>
> To: <linux-newbie@vger.kernel.org>
> Sent: Wednesday, September 10, 2003 11:58 AM
> Subject: Re: About PID...???!!!
>
>
> > At 11:21 AM 9/10/2003 -0400, John T. Williams wrote:
> > >They are assigned linearly, however once a pid is used, it is never
> reused
> > >until the machine reboots.
> >
> > This is not quite correct. The pid assignment process wraps, I *think*
at
> > 32767 (or maybe 65535). Next time around, the kernel skips over any pids
> > that are still in use from the last round of assignment.
> >
> > >A pid of 413 means that when that process was fork()'ed there had been
> 412
> > >other processes already created. But remember every time you type ls,
> you've
> > >run a process.
> > >
> > >413 isn't a large pid at all. My linux box which I very rarely reboot
is
> at
> > >PIDs that start at 20000
> > >
> > >I'm surprised that any program you start after the boot process is as
low
> as
> > >412.
> >
> > Whether that is surprising or not depends on what he uses the host for
> and,
> > naturally, on how recently it was rebooted. While my workstation is way
up
> > there (30180), my Linux-based router, which does not start new processes
> > very much, is only at pid 828.
> >
> > And, of course, there are persistent processes on any Linux host that go
> > back to the boot/init process ... starting with init itself (always pid
1)
> > and including long-lived daemons such as syslogd, klogd, and portmap;
> > pseudo processes that are actually run in the kernel (mostly [k*]
process
> > names); and getty proceses listening on VTs that never get logins.
> >
> >
> >
> > -
> > To unsubscribe from this list: send the line "unsubscribe linux-newbie"
in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at http://www.linux-learn.org/faqs
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.linux-learn.org/faqs

-
To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.linux-learn.org/faqs

Re: About PID...???!!!

[John T. Williams]

should not have used
----- Original Message ----- 
From: "John T. Williams" <jowillia@vt.edu>
To: "John T. Williams" <jtwilliams@vt.edu>; <linux-newbie@vger.kernel.org>
Sent: Wednesday, September 10, 2003 3:15 PM
Subject: Re: About PID...???!!!


> Alright Alright, I concede it does loop, I should have used the word
never.
> I'll change it to rarely and be done with it, in any case I think Silambu
> got his answer which briefly is:
>
> No PID = 412 doesn't mean there are 412 process currently running on your
> machine.
> Read the man page for ps to learn how to identify processes that are
> currently running.
>
> ----- Original Message ----- 
> From: "John T. Williams" <jowillia@vt.edu>
> To: <linux-newbie@vger.kernel.org>
> Sent: Wednesday, September 10, 2003 2:04 PM
> Subject: Re: About PID...???!!!
>
>
> > definitely higher then 2^16, I've got a process with the PID of 69917
> > I would guess MAX_INT which is 2^32 -1 = 4294967295
> >
> > ----- Original Message ----- 
> > From: "Ray Olszewski" <ray@comarre.com>
> > To: <linux-newbie@vger.kernel.org>
> > Sent: Wednesday, September 10, 2003 11:58 AM
> > Subject: Re: About PID...???!!!
> >
> >
> > > At 11:21 AM 9/10/2003 -0400, John T. Williams wrote:
> > > >They are assigned linearly, however once a pid is used, it is never
> > reused
> > > >until the machine reboots.
> > >
> > > This is not quite correct. The pid assignment process wraps, I *think*
> at
> > > 32767 (or maybe 65535). Next time around, the kernel skips over any
pids
> > > that are still in use from the last round of assignment.
> > >
> > > >A pid of 413 means that when that process was fork()'ed there had
been
> > 412
> > > >other processes already created. But remember every time you type ls,
> > you've
> > > >run a process.
> > > >
> > > >413 isn't a large pid at all. My linux box which I very rarely reboot
> is
> > at
> > > >PIDs that start at 20000
> > > >
> > > >I'm surprised that any program you start after the boot process is as
> low
> > as
> > > >412.
> > >
> > > Whether that is surprising or not depends on what he uses the host for
> > and,
> > > naturally, on how recently it was rebooted. While my workstation is
way
> up
> > > there (30180), my Linux-based router, which does not start new
processes
> > > very much, is only at pid 828.
> > >
> > > And, of course, there are persistent processes on any Linux host that
go
> > > back to the boot/init process ... starting with init itself (always
pid
> 1)
> > > and including long-lived daemons such as syslogd, klogd, and portmap;
> > > pseudo processes that are actually run in the kernel (mostly [k*]
> process
> > > names); and getty proceses listening on VTs that never get logins.
> > >
> > >
> > >
> > > -
> > > To unsubscribe from this list: send the line "unsubscribe
linux-newbie"
> in
> > > the body of a message to majordomo@vger.kernel.org
> > > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > > Please read the FAQ at http://www.linux-learn.org/faqs
> >
> > -
> > To unsubscribe from this list: send the line "unsubscribe linux-newbie"
in
> > the body of a message to majordomo@vger.kernel.org
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at http://www.linux-learn.org/faqs
>
> -
> To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> Please read the FAQ at http://www.linux-learn.org/faqs

-
To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.linux-learn.org/faqs