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

[Evgeniy Polyakov <johnpol@2ka.mipt.ru>]

On Thu, Oct 05, 2006 at 04:01:19PM +0200, Hans Henrik Happe (hhh@imada.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