Re: [Patch] Xargs: vary parallelism with SIGUSR1/2

[James Youngman]

On Sat, Jun 18, 2005 at 04:21:50AM -0700, John Gilmore wrote:
> I've been pleasantly surprised at how well xargs --max-procs N works.
> I've been using it with wget, and it lets me trivially parallelize
> some kinds of web spidering.  As more people get multiprocessor
> systems and multiprocessor cores, it will become even more useful.
> 
> The enclosed patch lets the parallelism of a long-running xargs be
> turned up or down with SIGUSR1 and SIGUSR2.  This lets me dynamically
> increase or decrease the network bandwidth I consume, without doing a
> cumbersome stop, rework the arguments, and restart cycle.
> 
> The cleanliness of the existing code made this an easy improvement to
> contribute.  I've also improved the documentation of --max-procs with
> a few examples.

This is a very interesting change.  The patch itself is exemplary in
terms of the inclusion of quality documentation, too.  Thanks.

As your documentation takes pains to point out, there is no simple way
to programmatically increase the parallelism to N, or set the degree
of parallelism to exactly N.  I can't think of a useful way of
providing that feature, useful though it would be.

I would like to apply your patch.  However, since this is a
significant change, I need to ask you to assign your copyright
interest in the change to the Free Software Foundation.  I'm obliged
to do this before applying the patch.  Would you be willing to do
this?  

If so, I'll put a copy of your patch at
http://savannah.gnu.org/patch/?group=findutils to make sure I don't
lose track of it while we wait for the copyright assignment process to
complete.

Two small nits with the patch:

1. It's probably better to reference signal(7) (which most Unix
   systems have) than signal(2) (which I suspect many don't).

2. There's no need to say "+ blah patch" in the version information - 
   if your patch is applied to findutils, it becomes part of the mainstream
   findutils release, and users can see the feature exists by reading the 
   documentation or the NEWS file.  I realise that putting that
   information into the version information would be helpful to you
   locally, of course.

Thanks again for your contribution.
James.