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

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Message-ID: <20070406104301.GB19755@lnx-holt.americas.sgi.com>
Date:	Fri, 6 Apr 2007 05:43:01 -0500
From:	Robin Holt <holt@....com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Chris Snook <csnook@...hat.com>, Robin Holt <holt@....com>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Jack Steiner <steiner@...ricas.sgi.com>
Subject: Re: init's children list is long and slows reaping children.

> So I think we have some options once we get the kernel threads out
> of the way.  Getting the kernel threads out of the way would seem
> to be the first priority.

I think both avenues would probably be the right way to proceeed.
Getting kthreads to not be parented by init would be an opportunity
for optimization.

I think organizing the zombie tasks to be easily reaped also has merit.
Rapidly forking/exiting processes like udevd during the boot of a
different machine were also shown to benefit significantly from this
patch.  That machine had 512 cpus and 4608 disk devices, we dropped the
device discovery under udevd by 30%.  This, honestly, surprised us.
It makes some sense now that I think about it.  This would be a case
where improving the zombie handling would be beneficial to more than
just kthreads.

Thanks,
Robin
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