[PATCHSET] blk-throttle: implement proper hierarchy support
Tejun Heo
tj at kernel.org
Thu May 2 18:49:53 UTC 2013
Hello,
On Thu, May 02, 2013 at 02:45:14PM -0400, Vivek Goyal wrote:
> I did not understand this point. In flat model, application issuing
> at configured page will not get penalized.
>
> This penalty is coming from the fact that we are moving bios after the
> wait and make them wait in another queue.
>
> In flat model there is no such problem. So to me, it is the problem
> of how hierarchical scheduling is implemented. In flat model, I did
> not have to deal with it.
But seen from the parent, the child isn't different from any other
issuer in flat hierarchy. It's just being repeated, so if you assume
a process which behaves in the exact same manner, that process would
get penalized too. e.g. imagine an application which throttles itself
and issues exactly 1MB/s amount of data in direct IO. It'd get
penalized the same way, right?
> Ok. Not having a perfect algorithm now is fine. We can always redo it
> later.
I think we can do source-based RR on bio_lists[] fetching which is
simple enough and should be able to avoid most of the problems, right?
Thanks.
--
tejun
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