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
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?
Thanks,
Peter
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