[Devel] Re: [PATCH 5/7] kiothrottled: throttle buffered (writeback) IO

[Gui Jianfeng]

Andrea Righi wrote:
> Together with cgroup_io_throttle() the kiothrottled kernel thread
> represents the core of the io-throttle subsystem.
> 
> All the writeback IO requests that need to be throttled are not
> dispatched immediately in submit_bio(). Instead, they are added into an
> rbtree by iothrottle_make_request() and processed asynchronously by
> kiothrottled.
> 
> A deadline is associated to each request depending on the bandwidth
> usage of the cgroup it belongs. When a request is inserted into the
> rbtree kiothrottled is awakened. This thread selects all the requests
> with an expired deadline and submit the bunch of selected requests to
> the underlying block devices using generic_make_request().

  Hi Andrea,

  What if an user issues "sync", will the bios still be buffered in the rb-tree?
  Do we need to flush the whole tree?

-- 
Regards
Gui Jianfeng

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