Re: [PATCH V5 05/17] blk-throttle: add upgrade logic for LIMIT_LOW state

Hello, again.

On Mon, Jan 09, 2017 at 01:40:53PM -0500, Tejun Heo wrote:

I think it'd be great to explain the above.  It was a bit difficult
for me to follow.  It's also interesting because we're tying state
transitions for both read and write together.  blk-throtl has been
handling reads and writes independently, now the mode switching from
low to max is shared across reads and writes.  I suppose it could be
fine but would it be complex to separate them out?  It's weird to make
this one state shared across reads and writes while not for others or
was this sharing intentional?

I thought more about it and as the low limit is regulated by latency,
it makes sense to make the state shared across reads and writes;
otherwise, IOs in one direction could easily mess up the other
direction.  Can you please document that this is an intentional design
and explain the rationale tho?

Thanks.

-- 
tejun