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RE: [Xen-devel] [PATCH] Console Daemon

To: "Rusty Russell" <rusty@xxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] [PATCH] Console Daemon
From: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Date: Wed, 3 Aug 2005 12:13:37 +0100
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Ian Pratt <Ian.Pratt@xxxxxxxxxxxx>, Robert Read <robert@xxxxxxxxxxxxx>, Christian Limpach <Christian.Limpach@xxxxxxxxxxxx>
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Thread-topic: [Xen-devel] [PATCH] Console Daemon
>       I don't think externally-supplied pages are necessary.  
> I was thinking of writing the page (or pages) into the store 
> immediately (since we don't need locks, or to wait for a 
> reply).  

We want to be able to get console output very early on, before xenbus
has come up.

However, it makes sense for xenbus to learn about the console buffer
once its up, as we'll want to use it (in future) for establishing
multiple tty's etc.

> I think we want more than one page because my boot 
> messages almost hit 8k to the first login prompt, and the 
> idea of requiring a console daemon repulses me.

It only really needs to be big enough to absorb all the messages before
Linux's console buffering code comes up, which isn't very much,
certainly <4KB.

My view is that we should continue using the same buffer once xenbus
comes up, hence there should be a simple multiplexing protocol.  


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