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Re: [Qemu-devel] Speed menu for GTK interfaace
From: |
Daniel P. Berrange |
Subject: |
Re: [Qemu-devel] Speed menu for GTK interfaace |
Date: |
Wed, 4 Jan 2017 15:51:16 +0000 |
User-agent: |
Mutt/1.7.1 (2016-10-04) |
On Wed, Jan 04, 2017 at 09:37:39AM +0100, Gerd Hoffmann wrote:
> Hi,
>
> > It is quite simple, there would be a 100% to a 1% menu item. It would look
> > like
> > this:
> >
> > Speed
> > -------
> > 100%
> > 90%
> > 80%
> > 70%
> > 60%
> > 50%
> > 40%
> > 30%
> > 20%
> > 10%
> > 1%
> >
> >
> > Each menu item would call cpu_throttle_set(). The value sent to this
> > function would
> > be determined like this:
> > speed = -1 * menu_number + 100;
>
> ok, that is the info I was looking for.
>
> > speed would be sent to the cpu_throttle_set() function. This function would
> > reduce
> > the CPU usage of QEMU on the host.
> >
> > Why would someone want to slow down QEMU?
> > - The user is using a laptop and don't want it to heat up.
>
> Sort-of makes sense, to keep the laptop quiet.
>
> > - The user wants to slow down a video game that is a little too challenging.
>
> Sure this would work? Throttling isn't a smooth slowdown, the cpu
> continues to run at full speed and is forced to pause now and then.
>
> > - The user wants to save energy.
>
> Pointless. Laptop may run longer, but your job needs more time to
> complete too. And constant vcpu start/stop isn't good to save power,
> the cpus can't enter deep sleep states then because of the frequent
> wakeups.
>
> > - The user wants to conduct some kind of stress test on a program and see
> > how
> > it handles under low cpu resources.
>
> Makes sense too.
>
> We already have "pause" in gtk, adding a "throttle" item next to it
> looks reasonable to me. I don't think it is that useful to have 10%
> steps in there, you probably never throttle 10% in practice. It's
> probably more useful to have something like "throttle -> off / 50% /
> 90% / 95% / 99%".
This feels like going down the slippery slope to turn the GTK frontend
into a full mgmt UI, which is something we've said we don't want todo
inside QEMU UI frontends. IMHO this kind of feature is best left to
external mgmt layers, like virt-manager/GNOME Boxes/etc. It is already
possible to timebox VMs CPU execution using cgroups quotas via libvirt.
Regards,
Daniel
--
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- [Qemu-devel] Speed menu for GTK interfaace, Programmingkid, 2017/01/01
- Re: [Qemu-devel] Speed menu for GTK interfaace, Gerd Hoffmann, 2017/01/03
- Re: [Qemu-devel] Speed menu for GTK interfaace, Programmingkid, 2017/01/03
- Re: [Qemu-devel] Speed menu for GTK interfaace, Gerd Hoffmann, 2017/01/04
- Re: [Qemu-devel] Speed menu for GTK interfaace, Programmingkid, 2017/01/04
- Re: [Qemu-devel] Speed menu for GTK interfaace,
Daniel P. Berrange <=
- Re: [Qemu-devel] Speed menu for GTK interfaace, Programmingkid, 2017/01/04
- Re: [Qemu-devel] Speed menu for GTK interfaace, Daniel P. Berrange, 2017/01/04
- Re: [Qemu-devel] Speed menu for GTK interfaace, Programmingkid, 2017/01/04
- Re: [Qemu-devel] Speed menu for GTK interfaace, Gerd Hoffmann, 2017/01/04