Subject: Re: [Ksummit-2008-discuss] Delayed interrupt work, thread pools
From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reply-To: benh@kernel.crashing.org
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>,
       ksummit-2008-discuss@lists.linux-foundation.org,
       Linux Kernel list <linux-kernel@vger.kernel.org>,
       Jeremy Kerr <jk@ozlabs.org>
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Date: Thu, 03 Jul 2008 20:31:26 +1000
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On Thu, 2008-07-03 at 03:12 -0700, Eric W. Biederman wrote:
> Benjamin Herrenschmidt <benh@kernel.crashing.org> writes:
> 
> > The question is: is that significantly less overhead than just spawning
> > a new full blown kernel thread ? enough to justify the complexity ? at
> > the end of the day, it means allocating a stack (which on ppc64 is still
> > 16K, I know it sucks)... 
> 
> I looked at this a while ago.  And right  now kernel_thread is fairly light.
> kthread_create has latency issues because we need to queue up a task on
> our kernel thread spawning daemon, and let it fork the child.  Needing
> to go via the kthread spawning daemon didn't look fundamental, just something
> that was a challenge to sort out.

Yes. I was thinking that if it becomes an issue, we could special case
something in the scheduler to pop them.

Ben.


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