linux-kernel - Re: [PATCH 2/3] make kthread

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Message-ID: <m1hcrjoowj.fsf@ebiederm.dsl.xmission.com>
Date:	Fri, 13 Apr 2007 17:06:20 -0600
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Oleg Nesterov <oleg@...sign.ru>,
	Davide Libenzi <davidel@...ilserver.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Roland McGrath <roland@...hat.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] make kthread_create() more scalable

Andrew Morton <akpm@...ux-foundation.org> writes:
>
> OK, I fixed that up.
>
> The next patch (make-kthread_stop-scalable) removes the find_task_by_pid()
> anyway.

Ok. Neat.  I still need to review these a little more I have a different
set of criteria, but it is interesting work..

> Our kthread creation performance will be pretty poor anyway, due to the
> need to do two (or more?) context switches.  If we ever need
> super-low-latency kernel thread creation (eg, on-demand threads for AIO)
> then that code would need to go direct to kernel_thread(), I guess.

Sure.  AIO is a little bit of a different beast as it is IO for user space.

If low latency is important for starting kernel threads the right
answer would be to dig into the code and have a version rewrite
kernel_thread so that we copied a reference process instead of the
current.

Right now my practical target is killing all of the kernel threads
started with kernel_thread that then call daemonize.  So we can remove
daemonize, as it is a serious maintenance hazard.  kthread needs just
a little bit more work to support that.

Eric
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