[ic] PreForkSingleFork?

Grant emailgrant at gmail.com
Wed Nov 7 12:18:15 EST 2007

> > Can anyone tell me what PreForkSingleFork does?  The docs don't
> > explain it and I can't follow the code.
> Standard PreFork uses the typical double-fork method in UNIX for
> generating daemons so as to avoid zombies (or more specifically needing
> to deal with them). However, forking IC daemons is relatively expensive.
> For most (if not all) sane, modern Unixen, you can avoid the relative
> expense of double forking by setting SIGCHLD to IGNORE in the master,
> which accomplishes roughly the same goal. It states, essentially, that
> the parent is not interested in the result of the child's process, so
> don't zombify my kids waiting for me to check on them.
> If you're running PreFork, you should always try PreForkSingleFork too
> to start. Only turn off PreForkSingleFork if something pathological
> happens (the most likely outcome being a slew of zombies piling up that
> are never reaped). Using it successfully creates the absolute minimal
> number of forks necessary.
> Mark

Thanks Mark.  I've enabled it with:

PreForkSingleFork Yes

So I should watch the process list for extra interchange processes?
How can I tell if they're zombies?

- Grant

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