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

To: Ian Pratt <m+Ian.Pratt@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] Console Daemon
From: Anthony Liguori <aliguori@xxxxxxxxxx>
Date: Tue, 02 Aug 2005 11:30:28 -0500
Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, Ian Pratt <Ian.Pratt@xxxxxxxxxxxx>, Christian Limpach <Christian.Limpach@xxxxxxxxxxxx>, Robert Read <robert@xxxxxxxxxxxxx>
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Ian Pratt wrote:

Today it buffers N bytes worth of data in memory regardless of whether the tty is connected (or reading from). How much it buffers is configurable via the store (by default the buffer has no limit so ensure console data is never lost).

If you connect and disconnect do you continue from where you left off or
get sent the last N bytes again?
You continue where you left off.

I think the former behaviour is definitely preferable, or at the very
least should be a configuration option.
What I was thinking is having the following layout in the store:


tty is obviously the tty for the domain (if tty doesn't exist, it means someone is connected already)

limit is the maximum amount of data (in bytes) that will be buffered

history is the amount of history (in bytes) that will be saved. When a client reconnects, they will first receive whatever's in the history.

Does this seem agreeable?

Please can you explain how tty's get allocated.
In the current scheme, a tty is allocated for each domain whenever data arrives for the domain or if consoled detects a new domain was created. It currently polls to see if new domains were created every second. You can avoid the race condition by signalling consoled which will break it out of it's select loop. Not very pretty but it solves the problem of something like xm create -c.


Anthony Liguori

Keeping a history wouldn't be a hard change. I'll submit some patches.


Anthony Liguori


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