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 <20200826175724.GQ3272@calimero.vinschen.de>
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Subject: Sv: Limit for number of child processes
Date: Thu, 27 Aug 2020 14:17:42 +0200
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From: Kristian Ivarsson via Cygwin <cygwin@cygwin.com>
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Hi Corinna

> > Dear cygwin folks
> >
> > It seems like there's a limit of the number of possible child
> > processes defined to 256 with 'NPROCS' in //winsup/cygwin/child_info.h
> > used in 'cprocs' in //winsup/cygwin/sigproc.cc
> >
> > 256 is quite few possible children in an enterprise environment and
> > perhaps the limit should be limited by the physical resources or
> possibly Windows ?
> 
> The info has to be kept available in the process itself so we need this
> array of NPROCS * sizeof (pinfo).
> 
> Of course, there's no reason to use a static array, the code could just as
> well use a dynamically allocated array or a linked list.  It's just not
> the way it is right now and would need a patch or rewrite.
> 
> As for the static array, sizeof pinfo is 64, so the current size of the
> array is just 16K.  We could easily bump it to 64K with NPROCS raised to
> 1024 for the next Cygwin release, at least on 64 bit.
> I don't think we should raise this limit for 32 bit Cygwin, which is kind
> of EOL anyway, given the massive restrictions.

I don't know the exact purpose of this and how the cprocs is used, but I'd
prefer something totally dynamic 7 days out of 7 or otherwise another limit
would just bite you in the ass some other day instead ;-)

A linked list could be used if you wanna optimize (dynamic) memory usage but
an (amortized) array would probably provide faster linear search but I guess
simplicity of the code and external functionality is the most important
demands for this choice

I'm looking forward for a future release where there's no children limit

Keep up the good work

Best regards,
Kristian

> Corinna
> 
> --
> Corinna Vinschen
> Cygwin Maintainer
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