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Old 7th October 2008
adamk adamk is offline
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Default qemu & kqemu

Is it possible to get qemu to make use of the kqemu kernel module?

I have both qemu-devel and kqemu-kmod-devel installed (and have tried with just the qemu and kqemu-kmod ports as well). However there is no noticeable difference in speed between qemu with or without the kqemu kernel module loaded. In addition, I can actually unload the kqemu kernel module while qemu is running a guest OS without any impact what-so-ever. I would assume that if qemu was actually using the acceleration provided by kqemu, I would get a message that the module was busy.

I have also noticed that loading the kqemu module does not result in a /dev/kqemu device being created like it does under Linux...

Any thoughts?

Adam
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Old 7th October 2008
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I know that a lot of the performance issues vary OS to OS. Google around for people's qemu guest tips. I know there are a few you can toss into a FreeBSD guest to make it run a bit smoother.

What particular guest are you running?
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Old 7th October 2008
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I've always assumed that if the kld was loaded when you started qemu, it'd be taken advantage of. All documentation I've read suggests that this is indeed the case.
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Old 7th October 2008
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Quote:
Originally Posted by Weaseal View Post
I know that a lot of the performance issues vary OS to OS. Google around for people's qemu guest tips. I know there are a few you can toss into a FreeBSD guest to make it run a bit smoother.

What particular guest are you running?
XP :-)

Adam
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Old 7th October 2008
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Quote:
Originally Posted by mdh View Post
I've always assumed that if the kld was loaded when you started qemu, it'd be taken advantage of. All documentation I've read suggests that this is indeed the case.
That's what I thought, too, but that doesn't appear to be the case. Shouldn't it complain when I try to unload the module while qemu is running? Or wouldn't qemu at least get majorly screwed up if it was actually using the kqemu accelerator? And the lack of a /dev/kqemu device really concerns me, though I have no idea if that is normal or not.

Adam
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Old 8th October 2008
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Are you using the '-kernel-kqemu' option when starting QEMU?

The QEMU docs state that you can check if the module is working by using the QEMU monitor command 'info kqemu'.
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Old 8th October 2008
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Quote:
Originally Posted by adamk View Post
Is it possible to get qemu to make use of the kqemu kernel module?
Code:
# kldload aio
# kldload kqemu
# qemu ...
Quote:
I have both qemu-devel and kqemu-kmod-devel installed (and have tried with just the qemu and kqemu-kmod ports as well). However there is no noticeable difference in speed between qemu with or without the kqemu kernel module loaded. In addition, I can actually unload the kqemu kernel module while qemu is running a guest OS without any impact what-so-ever. I would assume that if qemu was actually using the acceleration provided by kqemu, I would get a message that the module was busy.
If aio and kqemu modules are not loaded then you will get that warning:
Code:
# qemu ...
warning: aio not (kld)loaded, may cause `Invalid system call' traps on disk IO
Could not open '/dev/kqemu' - QEMU acceleration layer not activated: No such file or directory
Quote:
Any thoughts?
Try qemu (without -devel) maybe newest version tries to talk in some different way with kqemu while kqemu version in Ports my be outdated.
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Old 8th October 2008
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Sorry, user error. When I first built qemu from ports originally, I saw that it had a kqemu option. I, incorrectly, assumed that this would just build the kqemu kernel module. In fact, qemu has to be compiled to make use of the kernel module. So now it's working :-)

Unfortunately, the difference in speed isn't that great, but it's something at least.

Adam
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Old 9th October 2008
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My apologies beforehand.

A complete howto for setting up and running qemu on amd64, is one available?
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Old 9th October 2008
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Quote:
Originally Posted by Mr-Biscuit View Post
My apologies beforehand.

A complete howto for setting up and running qemu on amd64, is one available?
From QEMU Makefile:
Code:
ONLY_FOR_ARCHS= amd64 i386
So nothing changes here, you do all the things as you would do for i386.
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Old 9th October 2008
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Again, apologies beforehand.

Qemu on amd64 with kqemu uses tun tap with bridged networking.
I'm having trouble setting this up.
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