MAX limit of file descriptor

[michi1 at michaelblizek.twilightparadox.com]

Hi!

On 22:47 Sun 10 Feb     , Peter Teoh wrote:
> On Sun, Feb 10, 2013 at 8:29 PM,
> <michi1 at michaelblizek.twilightparadox.com>wrote:
> 
> > Hi!
> >
> > On 13:10 Sat 09 Feb     , horseriver wrote:
> > > hi:)
> > >
> > >    In one process ,what is the max number of opening file descriptor ?
> >
> > Type "ulimit -a" in your shell. On my system (debian) the default is 1024.
> >
> 
> Hi Michael, nice to see u again.
> 
> BTW, many of the parameters as reported by ulimit, also has to be taken
> with some doubts:
> 
> ulimit -a
> core file size          (blocks, -c) unlimited
> data seg size           (kbytes, -d) unlimited
> scheduling priority             (-e) 0
> file size               (blocks, -f) unlimited
> pending signals                 (-i) 47543
> max locked memory       (kbytes, -l) 64
> max memory size         (kbytes, -m) unlimited
> open files                      (-n) 1024
> pipe size            (512 bytes, -p) 8
> POSIX message queues     (bytes, -q) 819200
> real-time priority              (-r) 0
> stack size              (kbytes, -s) 8192
> cpu time               (seconds, -t) unlimited
> max user processes              (-u) 47543
> virtual memory          (kbytes, -v) unlimited
> file locks                      (-x) unlimited
> 
> the above is for Ubuntu 12.04 with 32-bit kernel (3.2.0) but of course we
> know that max file size has a limit - depending on whether it is ext2 or
> ext3 or ext4.   cannot remember the exact nos, but general conceptual
> level, there is a limit.

Well, ulimit is not really there to tell you what the system can handle. It
only tries to limit the ressources which can be used for stability/security
reasons.

Also, even if ulimit would want to tell you what the system can handle, the
interface is obviously not suited to export the file system limits when you
have more than one file system mounted.

File system limits:
http://en.wikipedia.org/wiki/Ext3
http://en.wikipedia.org/wiki/Ext4

> even for "CPU time"...it is limited by the underlying bit length of
> representation for time.   as usual...i don't know the details :-(, just
> concept.   sorry :-(.


ulimit -t 1
dd if=/dev/zero of=/dev/null

It seems cpu limit means that the process will be killed if it exceeds it.

	-Michi
-- 
programing a layer 3+4 network protocol for mesh networks
see http://michaelblizek.twilightparadox.com