Blkio: Apply two policies on one IO process

["Lina Lu" <lulina_nuaa@foxmail.com>]

Hi Vivek,
      As the weight and throttle policies are on different layers, someone can apply 
these two policies on one IO pid at one time. And the IO bandwidth will be controlled
with the more stringent policy.
      If someone first set two policies on one pid, then want to remove the weight
policy, he must first echo the pid to parent dir's tasks, then echo the throttle policy
to parent dir's blkio.throttle_xx_xx_device. These steps seen to be cumbersome.
      This is because the weight policy can be applied independence, but the throttle
policy is always accompany with the weight policy(default 500). I think it will be 
better that these policies are independent of each other. What is your opinion?
      Additional, do you recommend applying two policies on one IO process?

Thanks
Lina