Re: [Qemu-devel] [PATCH] upgrading emulated UART to 16550A

[Stefano Stabellini <stefano.stabellini@eu.citrix.com>]

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.