[syslog-ng] Re: syslog-ng Digest, Vol 6, Issue 10

[Valdis.Kletnieks at vt.edu]

On Sat, 08 Oct 2005 11:02:08 +0200, Roberto Nibali said:

> A simple stupid test would wrap the pids at 32k:

Right.  The fun starts when you do 'echo NNN > /proc/sys/kernel/pid_max' 
for some NNN > 32k.  On 32bit boxes 64K is the limit due to the /proc inode
wonkiness, but on 64bit kernels it's just a matter of how much RAM you have. ;)

> I knew that you could have 4Mio threads but I somehow wasn't aware that 
> you can have 4Mio forked processes. Since the Linux world changed to 
> NPTL we do not necessarily call clone() anymore when doing a 
> pthread_create() and thus we don't really fork() anymore, as with 
> linux_threads-0.10.

The numbers returned by getpid() and gettid() come out of the same PID space,
and the vast majority of programs aren't thread-aware, and get their PID
via fork() or vfork() anyhow...

> > # cut -f2 -d'[' /var/adm/seclog | cut -f1 -d']' | sort -nr | uniq | head
> > 191446
> > 191208
> > 191188
> > 191186
> > 191184
> > 191170
> > 191124
> > 191122
> > 191108
> > 191104
> 
> Mhh, these must be PIDs I reckon, since IIRC AIX can only handle 512 
> threads per process, right?

Yep. Those are indeed process IDs, coming out of binaries that I *know*
aren't multi-threaded...

> Thank you, Valdis, of course. Since I haven't actively remarked high 
> PIDs in my current development field I was still under the distinct 
> impression that PIDs are 16bit; I probably just overlooked the number of 
> digits in the logfiles all those years.

It's effectively an 'int' - any code that assumes a smaller range will
fail in the most interesting ways in the near future...  :)
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 226 bytes
Desc: not available
Url : http://lists.balabit.hu/pipermail/syslog-ng/attachments/20051008/dc4dfd39/attachment.pgp