Date: Thu, 22 Apr 2010 12:08:02 -0500
From: Robin Holt <holt@sgi.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>, Greg KH <gregkh@suse.de>,
       Rik van Riel <riel@redhat.com>, John Stoffel <john@stoffel.org>,
       Hedi Berriche <hedi@sgi.com>, Mike Travis <travis@sgi.com>,
       Ingo Molnar <mingo@elte.hu>, Jack Steiner <steiner@sgi.com>,
       Andrew Morton <akpm@linux-foundation.org>, Robin Holt <holt@sgi.com>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: [Patch 1/1] init: Provide a kernel start parameter to increase
 pid_max v2
Message-ID: <20100422170801.GZ5677@sgi.com>
References: <20100421165934.GN16427@zorg.emea.sgi.com>
 <4BCF336B.1050706@redhat.com>
 <19407.20109.308816.104856@stoffel.org>
 <20100421193350.GU16427@zorg.emea.sgi.com>
 <19407.23456.469074.256306@stoffel.org>
 <20100421222414.GA26241@suse.de>
 <4BCF80F2.2010906@redhat.com>
 <20100421232200.GA22877@suse.de>
 <20100422102852.72837494@lxorguk.ukuu.org.uk>
 <alpine.LFD.2.00.1004220743080.9086@i5.linux-foundation.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <alpine.LFD.2.00.1004220743080.9086@i5.linux-foundation.org>
User-Agent: Mutt/1.5.20 (2009-06-14)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1103
Lines: 33

> 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.

How about:

	pid_max_min = max(pid_max_min, 19 * num_possible_cpus());
	pid_max_baseline = 2048 * num_possible_cpus();

	if (pid_max < pid_max_baseline) {
		printk("We have %d CPUs, increasing pid_max to %d\n"...
		pid_max = pid_max_baseline;
	}


This would scale pid_max_min by a sane amount, leave the default value
of pid_max_min and pid_max untouched below 16 cpus and then scale both
up linearly beyond that.

Robin
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/