linux-kernel - Re: [patch 13/13] signalfd/timerfd/asyncfd v5 - KAIO asyncfd support (example/maybe-broken) ...

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Date:	Wed, 14 Mar 2007 17:27:33 -0700 (PDT)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Benjamin LaHaise <bcrl@...ck.org>
cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Suparna Bhattacharya <suparna@...ibm.com>,
	Zach Brown <zach.brown@...cle.com>
Subject: Re: [patch 13/13] signalfd/timerfd/asyncfd v5 - KAIO asyncfd support
 (example/maybe-broken) ...

On Wed, 14 Mar 2007, Davide Libenzi wrote:

> On Wed, 14 Mar 2007, Benjamin LaHaise wrote:
> 
> > On Wed, Mar 14, 2007 at 04:41:58PM -0700, Davide Libenzi wrote:
> > > Yeah, of course. I do not plan revolutions. Just asking if it's a possible 
> > > thing to do. I can mlock the userspace ring, if imposing that burden over 
> > > aio_complete() is seen as too heavy.
> > 
> > I'm not sure I follow what you're doing -- why isn't asyncfd merely calling 
> > io_getevents() instead of reinventing everything the ringbuffer does?  The 
> > aio ringbuffer is already locked in memory.  Fwiw, the aio ringbuffer was 
> > originally wired up to a file descriptor, but that gave way to the actual 
> > syscall in order to enforce proper typechecking and typical usage scenarios 
> > with timeouts.
> 
> The purpose of asyncfd is to provide a pollable (by the mean of 
> f_op->poll) device that can be hosted inside a standard select/poll/epoll 
> wait subsystem, and that, at the same time, provide a zero-copy way for 
> kernel code (KAIO and syslets/threadlets were my thought) to deliver 
> results to userspace.

But, yeah. It can end up calling io_getevents() instead of doing it's own 
thing. That'd make it even slimmer ;)



- Davide


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