On Jan 4, 2017, at 10:51 AM, Daniel P. Berrange wrote: > 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 > -- > |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| > |: http://libvirt.org -o- http://virt-manager.org :| > |: http://entangle-photo.org -o- http://search.cpan.org/~danberr/ :|
Are you saying that so we can use your Virt-manager? The thing is having more options is a good thing. If one solution doesn't work, another solution might. We don't live in a world with only one Linux distribution. We live in a world with many Linux distributions. We have the power of choice. There currently isn't a single QEMU front-end that runs on all three operating systems. Yes the Linux people do have Virt-manager, but what about the Windows and Macintosh people. They are not so fortunate. Enhancing the GTK front-end does not hurt any of the Virt-manager users at all. This change is just for the people who prefer the GTK front-end.
