linux-kernel - Re: [PATCH 2 of 4] Introduce i386 fibril scheduling

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Date:	Mon, 5 Feb 2007 14:34:48 -0800 (PST)
From:	Davide Libenzi <davidel@...ilserver.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	bert hubert <bert.hubert@...herlabs.nl>,
	Ingo Molnar <mingo@...e.hu>,
	Zach Brown <zach.brown@...cle.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-aio@...ck.org, Suparna Bhattacharya <suparna@...ibm.com>,
	Benjamin LaHaise <bcrl@...ck.org>
Subject: Re: [PATCH 2 of 4] Introduce i386 fibril scheduling

On Mon, 5 Feb 2007, Linus Torvalds wrote:

> On Mon, 5 Feb 2007, bert hubert wrote:
> > 
> > From my end as an application developer, yes please. Either make it
> > perfectly ok to have thousands of outstanding asynchronous system calls (I
> > work with thousands of separate sockets), or allow me to select/poll/epoll
> > on the "async fd".
> 
> No can do.
> 
> Allocating an fd is actually too expensive, exactly because a lot of these 
> operations are supposed to be a few hundred ns, and taking locks is simply 
> a bad idea.
> 
> But if you want to, we could have a *separate* "convert async cookie to 
> fd" so that you can poll for it, or something.
> 
> I doubt very many people want to do that. It would tend to simply be nicer 
> to do
> 
> 	async(poll);
> 	async(waitpid);
> 	async(.. wait foranything else ..)
> 
> followed by a
> 
> 	wait_for_async();
> 
> That's just a much NICER approach, I would argue. And it automatically 
> and very naturally solves the "wait for different kinds of events" 
> question, in a way that "poll()" never did (except by turning all events 
> into file descriptors or signals).

Bert, that was the first suggestion I gave to Zab. But then I realized 
that a multiplexed poll/epoll can be "hosted" in an async op, just like 
Linus showed above. Will work just fine IMO.




- Davide


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