linux-kernel - Re: [PATCH 3/3] pids: Make it possible to clone tasks with given pids

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Date:	Fri, 11 Nov 2011 08:06:09 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Pavel Emelyanov <xemul@...allels.com>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Cyrill Gorcunov <gorcunov@...nvz.org>,
	Glauber Costa <glommer@...allels.com>,
	Nathan Lynch <ntl@...ox.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Serge Hallyn <serue@...ibm.com>,
	Daniel Lezcano <dlezcano@...ibm.com>
Subject: Re: [PATCH 3/3] pids: Make it possible to clone tasks with given pids

Hello,

On Fri, Nov 11, 2011 at 7:58 AM, Pavel Emelyanov <xemul@...allels.com> wrote:
>> Hmm. It seems, we can make a simpler patch to achieve the (roughly)
>> same effect. Without touching copy_process/alloc_pid paths. What if
>> we simply add PR_SET_LAST_PID? (or something else).
>>
>> In this case the new init (created normally) read the pids from image
>> file and does prcrl(PR_SET_LAST_PID, pid-1) before the next fork.
>>
>> What do you think?
>
> This will make it impossible to fork() children on restore in parallel. And
> I don't want to lose this ability :(

It's highly unlikely that the ability to fork in parallel would
contribute to any meaningful speedup. That is not the critical path by
*far* and I don't think it's worth optimizing for. Forking in serial
and restoring the rest of states in parallel should be enough.

Thanks.

-- 
tejun
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