Le 23/09/2013 23:30, Bruce Dubbs a écrit : > Pierre Labastie wrote: >> Le 23/09/2013 18:10, Bruce Dubbs a écrit : >> >>> On the pdf of the above, it measured KVM I/O at about 60% of the host. >>> See pages 56-58. That seems to be consistent with my results. >>> >>> >> It is really amazing, because for the SBU benchmark, I consistently get not >> more than >> a 10 % increase of the timings with qemu. I tried also Arch Ubuntu on the VM, >> (everything -j1, with or without 'cache=writeback', on a qcow2 format. >> >> On this host (core i5), I get 158 (+-2) s on the host and 170 (+-5) s on the >> WM. >> Both with -j1 of course. >> >> Here is the qemu command I use: >> >> /usr/bin/qemu-system-x86_64 \ >> -monitor stdio \ >> -smp 4 -cpu Nehalem \ >> -soundhw ac97 \ >> -k fr \ >> -enable-kvm \ >> -m 3915 \ >> -drive file=/mnt/virtualfs/aqemu/blfs.qcow2,cache=writeback \ >> -cdrom /mnt/virtualfs/aqemu/grub-img.iso \ >> -boot order=c,menu=on \ >> -net nic,vlan=0,model=e1000 -net user,vlan=0,hostfwd=tcp::2222-10.0.2.9:22 \ >> -name "lfs" $* > Of the options above the only thing I can see that might affect things > are the line -smp 4 -cpu Nehalem. My system is: > > Intel(R) Core(TM)2 Duo CPU E8400 @3.00GHz > > so I can't specify -cpu Nehalem > > What do you get if you specify '-cpu host'? > > I can try specifying -smp 2 and still use make -j1 to see if that makes > a difference. > > I will wait a bit because the system is doing a full LFS build (all > tests) right now. It's chugging away at the Chapter 6 gcc tests right > now and the automake tests always take a while. > > As a side note, the boot time for my system is very fast: about 2 > seconds until starting the boot scripts and another 2 seconds to > complete them. > > -- Bruce I sometimes use -cpu core2duo and have not noticed any significant difference.
I would suspect that the -enable-kvm is the clue. I have tried without -enable-kvm, and as expected it becomes very slow. But thinking more about it, I would guess that -machine accel=kvm only enables acceleration for the cpu, while -enable-kvm "Enable[s] KVM full virtualization support" (citing the man page), which might include I/O. No time for testing now. Pierre -- http://linuxfromscratch.org/mailman/listinfo/lfs-dev FAQ: http://www.linuxfromscratch.org/faq/ Unsubscribe: See the above information page
