linux-kernel - Re: [PATCH] pidns: Make pid

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Message-ID: <4D789B64.9000603@parallels.com>
Date:	Thu, 10 Mar 2011 12:35:32 +0300
From:	Pavel Emelyanov <xemul@...allels.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Tejun Heo <tj@...nel.org>, Oleg Nesterov <oleg@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] pidns: Make pid_max per namespace

On 03/08/2011 02:58 AM, Andrew Morton wrote:
> On Thu, 03 Mar 2011 11:39:17 +0300
> Pavel Emelyanov <xemul@...allels.com> wrote:
> 
>> Rationale:
>>
>> On x86_64 with big ram people running containers set pid_max on host to 
>> large values to be able to launch more containers. At the same time 
>> containers running 32-bit software experience problems with large pids - ps
>> calls readdir/stat on proc entries and inode's i_ino happen to be too big 
>> for the 32-bit API.
>>
>> Thus, the ability to limit the pid value inside container is required.
>>
> 
> This is a behavioural change, isn't it?  In current kernels a write to
> /proc/sys/kernel/pid_max will change the max pid on all processes. 
> After this change, that write will only affect processes in the current
> namespace.  Anyone who was depending on the old behaviour might run
> into problems?

Hardly. If the behavior of some two apps depends on its synchronous change,
these two might want to run in the same pid namespace.

> Also: documentation.  Documentation/sysctl/kernel.txt would like an
> update.  And perhaps also the pidns documentation which we forgot to
> create :(

OK, I'll fix the existing docs.

Thanks,
Pavel
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