[Qemu-devel] migration speed setting.

[Yaodong Yang]

Hi everyone,

I know that inside the qemu monitor, we can set the max migration speed through " set_migration_speed 32 ". This '32' means 32MB.

My confusion is about the meaning of this 32MB. I checked the code and find that this '32MB' is the buffer size insde QemuFile, which include all the data submitted and read done(not transferred). If the buffer is full, the migration thread cannot send more requests to the underlying virtual disk. When there is some space inside this buffer, the migration thread can continue to send requests to the virtual disk.

However, there is another parameter list below:

/* Amount of time to allocate to each "chunk" of bandwidth-throttled

 * data. */

#define BUFFER_DELAY     100

#define XFER_LIMIT_RATIO (1000 / BUFFER_DELAY)

Does this mean that in the above case, the real buffer size is 3.2MB? If so, this buffer can only contain 3 chuncks. 

Could someone help me?

Thanks a lot!

Yaodong