On Mon, Feb 20, 2012 at 07:17:55PM +0100, Peter Lieven wrote: > Hi, > > I came a across an issue with a Windows 7 (32-bit) as well as with a > Windows 2008 R2 (64-bit) guest. > > If I transfer a file from the VM via CIFS or FTP to a remote machine, > i get very poor read performance (around 13MB/s). The VM peaks at 100% > cpu and I see a lot of insn_emulations and all kinds of exists in kvm_stat > > efer_reload 0 0 > exits 2260976 79620 > fpu_reload 6197 11 > halt_exits 114734 5011 > halt_wakeup 111195 4876 > host_state_reload 1499659 60962 > hypercalls 0 0 > insn_emulation 1577325 58488 > insn_emulation_fail 0 0 > invlpg 0 0 > io_exits 943949 40249 Hmm, too many of those. > irq_exits 108679 5434 > irq_injections 236545 10788 > irq_window 7606 246 > largepages 672 5 > mmio_exits 460020 16082 > mmu_cache_miss 119 0 > mmu_flooded 0 0 > mmu_pde_zapped 0 0 > mmu_pte_updated 0 0 > mmu_pte_write 13474 9 > mmu_recycled 0 0 > mmu_shadow_zapped 141 0 > mmu_unsync 0 0 > nmi_injections 0 0 > nmi_window 0 0 > pf_fixed 22803 35 > pf_guest 0 0 > remote_tlb_flush 239 2 > request_irq 0 0 > signal_exits 0 0 > tlb_flush 20933 0 > > If I run the same VM with a Ubuntu 10.04.4 guest I get around 60MB/s > throughput. The kvm_stats look a lot more sane. > > efer_reload 0 0 > exits 6132004 17931 > fpu_reload 19863 3 > halt_exits 264961 3083 > halt_wakeup 236468 2959 > host_state_reload 1104468 3104 > hypercalls 0 0 > insn_emulation 1417443 7518 > insn_emulation_fail 0 0 > invlpg 0 0 > io_exits 869380 2795 > irq_exits 253501 2362 > irq_injections 616967 6804 > irq_window 201186 2161 > largepages 1019 0 > mmio_exits 205268 0 > mmu_cache_miss 192 0 > mmu_flooded 0 0 > mmu_pde_zapped 0 0 > mmu_pte_updated 0 0 > mmu_pte_write 7440546 0 > mmu_recycled 0 0 > mmu_shadow_zapped 259 0 > mmu_unsync 0 0 > nmi_injections 0 0 > nmi_window 0 0 > pf_fixed 38529 30 > pf_guest 0 0 > remote_tlb_flush 761 1 > request_irq 0 0 > signal_exits 0 0 > tlb_flush 0 0 > > I use virtio-net (with vhost-net) and virtio-blk. I tried disabling > hpet (which basically illiminated the mmio_exits, but does not > increase > performance) and also commit (39a7a362e16bb27e98738d63f24d1ab5811e26a8 > ) - no improvement. > > My commandline: > /usr/bin/qemu-kvm-1.0 -netdev > type=tap,id=guest8,script=no,downscript=no,ifname=tap0,vhost=on > -device virtio-net-pci,netdev=guest8,mac=52:54:00:ff:00:d3 -drive format=host_device,file=/dev/mapper/iqn.2001-05.com.equallogic:0-8a0906-eeef4e007-a8a9f3818674f2fc-lieven-windows7-vc-r80788,if=virtio,cache=none,aio=native > -m 2048 -smp 2 -monitor tcp:0:4001,server,nowait -vnc :1 -name > lieven-win7-vc -boot order=dc,menu=off -k de -pidfile > /var/run/qemu/vm-187.pid -mem-path /hugepages -mem-prealloc -cpu > host -rtc base=localtime -vga std -usb -usbdevice tablet -no-hpet > > What further information is needed to debug this further? > Which kernel version (looks like something recent)? Which host CPU (looks like something old)? Which Windows' virtio drivers are you using? Take a trace like described here http://www.linux-kvm.org/page/Tracing (with -no-hpet please). Try to use -cpu host,+x2apic. It may help Linux guest performance. -- Gleb. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
