linux-kernel - Re: init's children list is long and slows reaping children.

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Message-ID: <20070406194329.GB21322@elte.hu>
Date:	Fri, 6 Apr 2007 21:43:29 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Robin Holt <holt@....com>, Chris Snook <csnook@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: init's children list is long and slows reaping children.


* Oleg Nesterov <oleg@...sign.ru> wrote:

> > I'd almost prefer to just not add kernel threads to any parent 
> > process list *at*all*.
> 
> Yes sure, I didn't argue with that. However, "->exit_state = -1" does 
> matter, we can't detach process unless we make it auto-reap.

> Off course, we also need to add preparent_to_init() to kthread() and 
> (say) stopmachine(). Or we can create kernel_thread_detached() and 
> modify callers to use it.

this isnt a kernel-thread special case. The right solution IMO is to 
first migrate wait4()'s ->children use over to a new p->exiting_children 
list and then to gradually get rid of all remaining uses of p->children. 
(the first patch of which i sent a few minutes ago)

that way wait4() will be sped up, and quite dramatically i believe. No 
need to deal with kthreads here at all - those just wont ever show up in 
the ->exiting_children list. Am i missing something?

	Ingo
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