Re: [Qemu-devel] [PATCH] block: add the support to drain throttled requests

[Paolo Bonzini]

Il 20/03/2012 10:40, Zhi Yong Wu ha scritto:
> HI, Kevin,
> 
> We hope that I/O throttling can be shipped without known issue in QEMU
> 1.1, so if you are available, can you give this patch some love?

I'm sorry to say this, but I think I/O throttling is impossible to save.
 As it is implemented now, it just cannot work in the presence of
synchronous I/O, except at the cost of busy waiting with the global
mutex taken.  See the message from Stefan yesterday.

Unfortunately I don't have any solution for this, except perhaps
disabling throttling around synchronous I/O.

Paolo