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

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Message-ID: <20100421201216.GW16427@zorg.emea.sgi.com>
Date:	Wed, 21 Apr 2010 21:12:17 +0100
From:	Hedi Berriche <hedi@....com>
To:	Greg KH <gregkh@...e.de>
Cc:	Alan Cox <alan@...rguk.ukuu.org.uk>, Mike Travis <travis@....com>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	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

On Wed, Apr 21, 2010 at 20:52 Greg KH wrote:
| On Wed, Apr 21, 2010 at 08:12:13PM +0100, Hedi Berriche wrote:
| > Let's also not forget all those ephemeral user space tasks (udev and the likes)
| > that will be spawned at boot time on even large systems with even more
| > thousands of disks, arguably one might consider hack initrd and similar to work
| > around the problem and set pid_max as soon as /proc becomes available but it's
| > a bit of a PITA.
| 
| udev should properly handle large numbers of cpus and the tasks that it
| spawns so as to not overload things.  If not, and you feel it is
| creating too many tasks, please let the udev developers know and they
| will be glad to work with you on this issue.

Just to be clear here --and be done with the udev parenthesis-- we kind of need
udev to take advantage of the fact that there's a large number of CPUs on the
machine especially on in the case of a config with thousands of disks, as that
shortens the time required to have a box in a working state with all disks
available and all.

IOW, I am not after throttling or serialising udev, just mentioned it as an
example of user space beast that can contribute --in the current state of things--
to the need of having a large number of pid_max on certain configurations.

That said I do realise that bit too should be looked at and any problems, as you
quite rightly pointed out, should be discussed with the udev chaps.

Cheers,
Hedi.
-- 
Be careful of reading health books, you might die of a misprint.
	-- Mark Twain
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