Re: Child process limits cumulative or instantaneous?
Re: Child process limits cumulative or instantaneous?
- Subject: Re: Child process limits cumulative or instantaneous?
- From: mm w <email@hidden>
- Date: Fri, 27 Feb 2009 08:37:22 -0800
ERRORS
Fork() will fail and no child process will be created if:
[EAGAIN] The system-imposed limit on the total number of pro-
cesses under execution would be exceeded. This limit
is configuration-dependent.
[EAGAIN] The system-imposed limit MAXUPRC (<sys/param.h>) on
the total number of processes under execution by a
single user would be exceeded.
[ENOMEM] There is insufficient swap space for the new process.
On Fri, Feb 27, 2009 at 8:13 AM, Ralph Castain <email@hidden> wrote:
> Hello folks
>
> I'm the run-time developer for Open MPI and am encountering a resource
> starvation problem that I don't understand. What we have is a test program
> that spawns a child process, exchanges a single message with it, and then
> the child terminates. We then spawn another child process and go through the
> same procedure.
>
> This paradigm is typical of some of our users who want to build
> client-server applications using MPI. In these cases, they want the job to
> run essentially continuously, but have a rate limiter in their application
> so only one client is alive at any time.
>
> We have verified that the child processes are properly terminating. We have
> monitored and observed that all file descriptors/pipes are being fully
> recovered after each cycle.
>
> However, after 263 cycles, the fork command returns an error indicating that
> we have exceeded the number of allowed child processes for a given process.
> This is fully repeatable, yet the number of child processes in existence at
> any time is 1, as verified by ps.
>
> Do you have any suggestions as to what could be causing this problem? Is the
> limit on child processes a cumulative one, or instantaneous?
>
> Appreciate any help you can give
> Ralph
>
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--
-mmw
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