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From: Paul Brook <paul@codesourcery.com>
To: qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] high resolution timer question
Date: Tue, 11 Dec 2007 01:17:35 +0000	[thread overview]
Message-ID: <200712110117.36363.paul@codesourcery.com> (raw)
In-Reply-To: <475D7EFE.7060309@codemonkey.ws>

> > 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.

Paul

  reply	other threads:[~2007-12-11  1:17 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-12-10 12:59 [Qemu-devel] high resolution timer question Robert Reif
2007-12-10 15:16 ` Arnon Gilboa
2007-12-10 17:51 ` Blue Swirl
2007-12-10 18:01   ` Anthony Liguori
2007-12-11  1:17     ` Paul Brook [this message]
2007-12-12  1:02   ` Robert Reif
2007-12-12  2:21     ` Robert Reif
2007-12-12  3:23       ` Robert Reif

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