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

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Date:	Wed, 21 Apr 2010 10:54:22 -0700
From:	Mike Travis <travis@....com>
To:	Rik van Riel <riel@...hat.com>
CC:	Hedi Berriche <hedi@....com>, Alan Cox <alan@...rguk.ukuu.org.uk>,
	Ingo Molnar <mingo@...e.hu>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	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



Rik van Riel wrote:
> On 04/21/2010 12:59 PM, Hedi Berriche wrote:
>> On Wed, Apr 21, 2010 at 10:20 Alan Cox wrote:
>> |>  of 32k will not be enough.  A system with 1664 CPU's, there are 
>> 25163 processes
>> |>  started before the login prompt.  It's estimated that with 2048 
>> CPU's we will pass
>> |
>> | Is that perhaps the bug not the 32K limit?
>>
>> Doubt it: I just checked on an *idle* 1664 CPUs system and I can see 
>> 26844
>> tasks, all but few being kernel threads.
> 
> That is 15 kernel threads per CPU.
> 
> Reducing the number of kernel threads sounds like a
> useful thing to do.

I'm doing more research but all the udev modprobes seem to spawn
quite a few tasks.  And even though they go away, when the pid
pool is limited, I'm guessing many of them are waiting.

On the last test I did yesterday, the pid # was up in the 77000
range at the login prompt (I started the 1664 cpu system with
pid_max=128k).
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