Windows7 on KVM consumes large amount of host CPU while apparently idle
I have a Windows 7 guest running under qemu-kvm-0.15.0 (kernel 3.0-ARCH). Despite the guest showing as relatively (2-3% in taskmgr) idle, the VM never seems to drop below 25% host CPU, and an strace on the qemu process shows a large amount of time being spent in futex():
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$ sudo strace -f -c -p 27004 & sleep 60 && kill %1 Code:
/usr/bin/qemu-kvm -S -M pc-0.14 -enable-kvm -m 1024 Chris |
You need to install Windows in qemu with the '-no-acpi' qemu option, otherwise the system burns CPU communicating with what it thinks is the ACPI BIOS. I don't know of any way to disable this after installation.
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I don't use KVM -- VirtualBox instead -- and I notice constant CPU activity in both cores, varying from 3%-5% up to about 24% periodically with a Win7 64-bit guest; I never see anywhere near that activity when Slackware-64 is just sitting the mumbling to itself. And, XP is significantly worse than Win7 as far as CPU activity. It just appears that Windows-whatever-version is a hog no matter what you do (keep in mind that Windows is always doing some blasted thing or other that uses cycles).
As I'm writhing this both cores at at 50% +. Why, I do not know. Can't really advise you what to do other than perhaps giving it more RAM and see if that helps (so it's not stumbling over its own feet all the time). If you've got 4G or more in the box, let it have 2G -- it is a hog and that's what I've done to alleviate some of the problems. I keep an eye on things with GKrellM, which is a kind of nifty monitor utility that displays your CPU(s), processes, disk activty, Ethernet activity, memory use, swap use and your can add battery status, fans, temperature and all kinds of stuff if they're available on your system. Might be worth a little time to either start that up (if it's already on you system) or get it from http://members.dslextreme.com/users/...m/gkrellm.html. I look forward to the day that I can completely dump Microsoft forever, bu tin the meantime... Hope this helps some. |
@tronayne I don't know if you've seen this.
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Well, so far, it seems to work for me -- I only use Win7 for Stamp.com, Family Tree Maker and Turbotax -- and, of course, the almost weekly "critical updates." Dammit, I do hate Windows. Sigh. |
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Just tried with 2GB, no difference I'm afraid - still burning far too many CPU cycles.
Chris |
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