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Date: Tue, 05 Aug 2008 15:17:46 +0100
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
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Subject: Re: [Qemu-devel] [PATCH] upgrading emulated UART to 16550A
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To: Thiemo Seufer <ths@networkno.de>
Cc: Ian Jackson <Ian.Jackson@eu.citrix.com>, qemu-devel@nongnu.org

Thiemo Seufer wrote:

>> +/* Rate limit serial requests so that e.g. grub on a serial console
>> +   doesn't kill dom0.  Simple token bucket.  If we get some actual
>> +   data from the user, instantly refil the bucket. */
>> +
>> +/* How long it takes to generate a token, in nanoseconds. */
>> +#define TOKEN_PERIOD 1000000
>> +/* Maximum and initial size of token bucket */
>> +#define TOKENS_MAX 100000
> 
> This token business probably needs a bit more explanation, at a glance
> I didn't figure out what it is meant to do (and why the constants above
> are good).
> 

The token bucket was introduced to rate limit serial requests, mainly
for performance reasons (grub makes too many requests).
However I realize that conceptually it doesn't belong to qemu, so I am
going to send another patch soon without the token bucket.