[Codel] [RFC PATCH] codel: ecn mark at target
eric.dumazet at gmail.com
Mon Aug 6 16:01:09 EDT 2012
On Mon, 2012-08-06 at 12:09 -0700, Andrew McGregor wrote:
> On 6/08/2012, at 10:50 AM, Dave Taht <dave.taht at gmail.com> wrote:
> > This discussion is getting mildly off-track. My intent in posting this patch
> > was to prove how wrong the "ecn mark at target" idea was by example,
> > and in doing so, shed light on those new to codel, on how the algorithm
> > actually works, and to encourage those that didn't grok it, to read and
> > run the code in whatever scenarios would help more people to
> > grokking in fullness.
> > I hadn't expected to twiddle a bug!
> Well, so drop at target is wrong wrt deployed TCPs. Ok, fine.
> So, instead, how about this: mark instead of dropping, but only for
> the first few iterations around the while loop in dequeue (so that
> huge backlogs can be drained). The question then is, how many is a
> few? I suppose that can be answered empirically.
Lets take the analogy with RED.
Once a MAX_THRESH was reached, it did a hard_mark.
So we could choose a threshold to drop instead of marking.
Possible easy choices :
1) A threshold on sojourn time. For example force_drop = 2 * target
2) A threshold on 'count'. For example force_drop if count > 1000
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