linux-kernel - Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3

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Message-ID: <20070228161413.GA4319@ucw.cz>
Date:	Wed, 28 Feb 2007 16:14:14 +0000
From:	Pavel Machek <pavel@....cz>
To:	Evgeniy Polyakov <johnpol@....mipt.ru>
Cc:	Theodore Tso <tytso@....edu>, Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ulrich Drepper <drepper@...hat.com>,
	linux-kernel@...r.kernel.org,
	Arjan van de Ven <arjan@...radead.org>,
	Christoph Hellwig <hch@...radead.org>,
	Andrew Morton <akpm@....com.au>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Zach Brown <zach.brown@...cle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Davide Libenzi <davidel@...ilserver.org>,
	Jens Axboe <jens.axboe@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3

Hi!

> > I think what you are not hearing, and what everyone else is saying
> > (INCLUDING Linus), is that for most programmers, state machines are
> > much, much harder to program, understand, and debug compared to
> > multi-threaded code.  You may disagree (were you a MacOS 9 programmer
> > in another life?), and it may not even be true for you if you happen
> > to be one of those folks more at home with Scheme continuations, for
> > example.  But it is true that for most kernel programmers, threaded
> > programming is much easier to understand, and we need to engineer the
> > kernel for what will be maintainable for the majority of the kernel
> > development community.
> 
> I understand that - and I totally agree.
> But when more complex, more bug-prone code results in higher performance
> - that must be used. We have linked lists and binary trees - the latter

No-o. Kernel is not designed like that.

Often, more complex and slightly faster code exists, and we simply use
slower variant, because it is fast enough.

10% gain in speed is NOT worth major complexity increase.
							Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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