Re: disappointing speed with virtio_blk

[Gerd von Egidy <lists@egidy.de>]

Hi Marcelo,

thanks for the quick reply.

> When the hang happens, can you run kvm-stat --once (script can be found
> kvm-66 directory) and paste the result?

efer_reload                    0         0
exits                    4943909      2036
fpu_reload                222178         0
halt_exits                896464       999
halt_wakeup                17690         0
host_state_reload        2279013      1027
insn_emulation           2640886      1001
insn_emulation_fail            0         0
invlpg                         0         0
io_exits                  396350        28
irq_exits                 200020         1
irq_window                     0         0
mmio_exits                900583         0
mmu_cache_miss             54441         0
mmu_flooded                63313         0
mmu_pde_zapped             46114         0
mmu_pte_updated           554813         0
mmu_pte_write             639377         0
mmu_recycled                   0         0
mmu_shadow_zapped          63313         0
pf_fixed                 1205697         0
pf_guest                   92134         0
remote_tlb_flush               1         0
request_irq                    0         0
signal_exits                   1         0
tlb_flush                 609240         5

> Can you confirm that reverting the patch fixes it?

It seems to be some kind of race condition, it doesn't completely hang the 
system always at the same position but probably brings the io to a halt at 
some time.

I just got it to boot, but when running bonnie++ it halted at some time. The 
kvm_stat output above is from that one. I was still able to type in stuff
at the console but the console couldn't break the system call bonnie was in.

Booting a qemu-kvm without the patch completely fixes these problems.

Kind regards,

Gerd

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