linux-kernel - Re: [take19 1/4] kevent: Core files.

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Date:	Thu, 5 Oct 2006 18:15:56 +0400
From:	Evgeniy Polyakov <johnpol@....mipt.ru>
To:	Hans Henrik Happe <hhh@...da.sdu.dk>
Cc:	Eric Dumazet <dada1@...mosbay.com>,
	Ulrich Drepper <drepper@...il.com>,
	lkml <linux-kernel@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Ulrich Drepper <drepper@...hat.com>,
	Andrew Morton <akpm@...l.org>, netdev <netdev@...r.kernel.org>,
	Zach Brown <zach.brown@...cle.com>,
	Christoph Hellwig <hch@...radead.org>,
	Chase Venters <chase.venters@...entec.com>,
	Johann Borck <johann.borck@...sedata.com>
Subject: Re: [take19 1/4] kevent: Core files.

On Thu, Oct 05, 2006 at 04:01:19PM +0200, Hans Henrik Happe (hhh@...da.sdu.dk) wrote:
> > And what happens when there are 3 empty at the beginning and \we need to
> > put there 4 ready events?
> 
> Couldn't there be 3 areas in the mmap buffer:
> 
> - Unused: entries that the kernel can alloc from.
> - Alloced: entries alloced by kernel but not yet used by user. Kernel can 
> update these if new events requires that.
> - Consumed: entries that the user are processing.
> 
> The user takes a set of alloced entries and make them consumed. Then it 
> processes the events after which it makes them unused. 
> 
> If there are no unused entries and the kernel needs some, it has wait for free 
> entries. The user has to notify when unused entries becomes available. It 
> could set a flag in the mmap'ed area to avoid unnessesary wakeups.
> 
> The are some details with indexing and wakeup notification that I have left 
> out, but I hope my idea is clear. I could give a more detailed description if 
> requested. Also, I'm a user-level programmer so I might not get the whole 
> picture.

This looks good on a picture, but how can you put it into page-based
storage without major and complex shared structures, which should be
properly locked between kernelspace and userspace?

> Hans Henrik Happe

-- 
	Evgeniy Polyakov
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