linux-kernel - Re: [Patch 1/1] init: Provide a kernel start parameter to increase pid

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Message-ID: <20100425071606.GB1275@ucw.cz>
Date:	Sun, 25 Apr 2010 09:16:06 +0200
From:	Pavel Machek <pavel@....cz>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, Greg KH <gregkh@...e.de>,
	Rik van Riel <riel@...hat.com>,
	John Stoffel <john@...ffel.org>, Hedi Berriche <hedi@....com>,
	Mike Travis <travis@....com>, Ingo Molnar <mingo@...e.hu>,
	Jack Steiner <steiner@....com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Robin Holt <holt@....com>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [Patch 1/1] init: Provide a kernel start parameter to increase
 pid_max v2

Hi!

> > > Distros don't want to take a patch that adds a new boot param that is
> > > not accepted upstream, otherwise they will be stuck forward porting it
> > > from now until, well, forever :)
> > 
> > So for an obscure IA64 specific problem you want the upstream kernel to
> > port it forward forever instead ?
> 
> Ehh. Nobody does ia64 any more. It's dead, Jim.
> 
> This is x86. SGI finally long ago gave up on the Intel/HP clusterf*ck.
> 
> Which I'm not entirely sure makes the case for the kernel parameter much 
> stronger, though. I wonder if it's not more appropriate to just have a 
> total hack saying
> 
> 	if (max_pids < N * max_cpus) {
> 		printk("We have %d CPUs, increasing max_pids to %d\n");
> 		max_pids = N*max_cpus;
> 	}
> 
> where "N" is just some random fudge-factor. It's reasonable to expect a 
> certain minimum number of processes per CPU, after all.

Issue with max_pids is that it can break userspace, right?

At that point it seems saner to require a parameter --- just adding
cpus to the system should not do it... 

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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