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

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Date:	Sat, 3 Mar 2007 13:27:45 +0300
From:	Evgeniy Polyakov <johnpol@....mipt.ru>
To:	Davide Libenzi <davidel@...ilserver.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Pavel Machek <pavel@....cz>,
	Theodore Tso <tytso@....edu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ulrich Drepper <drepper@...hat.com>,
	Linux Kernel Mailing List <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>,
	Jens Axboe <jens.axboe@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch 00/13] Syslets, "Threadlets", generic AIO support, v3

On Fri, Mar 02, 2007 at 09:28:10AM -0800, Davide Libenzi (davidel@...ilserver.org) wrote:
> On Fri, 2 Mar 2007, Evgeniy Polyakov wrote:
> 
> > do we really want to have per process signalfs, timerfs and so on - each 
> > simple structure must be bound to a file, which becomes too cost.
> 
> I may be old school, but if you ask me, and if you *really* want those 
> events, yes. Reason? Unix's everything-is-a-file rule, and being able to 
> use them with *existing* POSIX poll/select. Remember, not every app 
> requires huge scalability efforts, so working with simpler and familiar 
> APIs is always welcome.
> The *only* thing that was not practical to have as fd, was block requests. 
> But maybe threadlets/syslets will handle those just fine, and close the gap.

That means that we bind very small object like timer or signal to the
whoe file structure - yes, as I stated - it is doable, but do we really
have to create a file each time create_timer() or signal() is called?
Signals as a filesystem are limited in that regard that we need to
create additional structures to have signal number<->private data
relations.
I designed kevent to be as small as possible, so I removed file binding
idea first. I do not say it is wrong or epoll (and threadlets) are broken 
(fsck, I hope people do understand that), but as is it can not handle
that scenario, so it must be extended and/or a lot of other stuff
written to be compatible with epoll design. Kevent has different design
(which allows to work with old one though - there is a patch to
implement epoll over kevent).

> - Davide
> 

-- 
	Evgeniy Polyakov
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