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Re: [Qemu-devel] high resolution timer question

From: Paul Brook
Subject: Re: [Qemu-devel] high resolution timer question
Date: Tue, 11 Dec 2007 01:17:35 +0000
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> > I think the throttling should be done at CharDriver level so that all
> > targets and also other devices, like parallel ports (SUNW,bpp anyone?)
> But the timing is entirely a concept of the hardware devices.  It seems
> like it would be easier to just add a growable buffer, and then setup a
> timer in each device that reads from the buffer.

I don't see why timing is device specific. The mechanisms for setting the 
speed are device specific, but the throttling should not be.
You may need to augment the char driver API to support outgoing throttling.

I'd also like to request that this feature be disabled by default. As I've 
mentined several times before qemu is not cycle accurate, so any attempt to 
do "accurate" timing is completely arbitrary.

In practice I'd expect any throttling is probably going to have to be fairly 
coarse grained because the emulated cpu speed is extremely 
variable/irregular, and you're limited by host timer resolution.


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