Re: [Qemu-devel] QEMU 1.1.2: block IO throttle might occasionally freeze running process's IO to zero

[Fam Zheng]

On Thu, 12/01 12:07, Bob Chen wrote:
> Test case:
> 
> 1. QEMU 1.1.2
> 2. Run fio inside the vm, give it some pressure. Watch the realtime
> throughput
> 3. block_set_io_throttle drive_2 100000000 0 0 2000 0 0         # throttle
> bps and iops, any value
> 4. Observed that the IO is very likely to freeze to zero. The fio process
> stuck!
> 5. Kill the former fio process, start a new one. The IO turns back to normal
> 
> Didn't reproduce it with QEMU 2.5.
> 
> 
> Actually I'm not wishfully thinking the community would help fix this bug
> on such an ancient version. Just hope someone can tell me what is the root
> cause. Then I have to evaluate whether I should move to higher version
> QEMU, or fix this bug on 1.1.2 in-place(if it is a small one).

The throttling implementation is completely refreshed so I think it's not easy
to suggest a root cause for you.

Fam