AIX File Descriptor limitation???

[Timasmith]

Hi,

Someone described to me that using pipes for an application is very
bad and not scalable at all.

They said that AIX has a limit of 1024 (or something close) file
descriptors and while any file is open a descriptor is used, such that
you can only have 1024 files open at once.

They said that just the existence of a pipe alone is enough to use up
a file descriptor - and so competing with the number of files that can
be open.

It seems a little incredulous to me that only a relatively small
number of files can be opened at once, or even that a relativelty
small number of pipes can be used.

Can anyone confirm or deny?

[Mark Taylor]

This is AIX 5.3 btw...

$ grep OPEN_MAX /usr/include/sys/limits.h
#define OPEN_MAX 65534 /* max num of files per process */

HTH
Mark Taylor

[Mark Taylor]

there is also a ulimit on the user level "nofiles" which defaults to
2000, you can of course increase this ..

Rgds
Mark Taylor

[Timasmith]

> > Can anyone confirm or deny?- Hide quoted text -
>
> - Show quoted text -

is that per PROCESS?? so you could have 10 processes, each with 50,000
file descriptors open (in theory?)

[Gary R. Hook]

Timasmith wrote:
> On Jan 30, 10:33 am, "Mark Taylor" <m...@talk21.com> wrote:
>> This is AIX 5.3 btw...
>>
>> $ grep OPEN_MAX /usr/include/sys/limits.h
>> #define OPEN_MAX 65534 /* max num of files per process */
>>

> is that per PROCESS?? so you could have 10 processes, each with 50,000
> file descriptors open (in theory?)
>

There's a system-wide limit as well, but it's very large.

Essentially, you were misinformed. The practical limit is
quite high, is indeed per-process.

[Lőrinczy Zsigmond]

Timasmith wrote:
> Hi,
>
> Someone described to me that using pipes for an application is very
> bad and not scalable at all.
>
> They said that AIX has a limit of 1024 (or something close) file
> descriptors and while any file is open a descriptor is used, such that
> you can only have 1024 files open at once.

When we had similiar problem, we found a way to set the limit (somewhere
in smitty, I don't remember), but only for all users globally
unlike linux where you can set different limits for different users.

[Mark Taylor]

> is that per PROCESS?? so you could have 10 processes, each with 50,000
> file descriptors open (in theory?)

yup .. the system wide limit I am assuming is based on the number of
process slots in the proc table ?

$ grep PROCSHIFT /usr/include/sys/proc.h
#define PROCSHIFT 18 /* number of bits in proc index */

2^18==262144
262144*65534==17179344896

Although, somthing else will probably break before you hit this
limit :)

Gary might know .. has this limit been reached/tested in dev or is it
theoretical based on the architecture ? or is the supported limit the
actual number reached/tested in dev ?

Rgds
Mark Taylor

[ColombianJoker]

AIX has *per user* limits, you can look at them in /etc/security/
limits, and these are changeable with "chuser".

[Gary R. Hook]

Mark Taylor wrote:
>> is that per PROCESS?? so you could have 10 processes, each with 50,000
>> file descriptors open (in theory?)
>
> yup .. the system wide limit I am assuming is based on the number of
> process slots in the proc table ?
>

I don't know what the system-wide limit is any more (it was 1 M in
AIX 4.3.1). Whatever it is, I'm sure that some testing has taking
place, and that the upper limit is by design with attention to
scalability.

[Mark Taylor]

> I don't know what the system-wide limit is any more (it was 1 M in
> AIX 4.3.1). Whatever it is, I'm sure that some testing has taking
> place, and that the upper limit is by design with attention to
> scalability.

Thanks for your response..