On 2018-08-22 04:10, Toke Høiland-Jørgensen wrote:
Rajkumar Manoharan <rmanohar@xxxxxxxxxxxxxx> writes:
On 2018-08-21 05:24, Toke Høiland-Jørgensen wrote:
Rajkumar Manoharan <rmanohar@xxxxxxxxxxxxxx> writes:
[...]
Yeah, but the fairness comes from all TXQs being given the *same
amount*
of deficit increase. I.e., with reorder_txq() there needs to be a
guarantee that it is called the same number of times for all active
TXQs. Which is what the round-robin scheduling ensures in next_txq().
Understood.
As mentioned earlier, next_txq() can not be used for fetching txq
directly. So reorder_txq() needs to take care of refilling txq after
serving them.
Yeah, I got that; but see above. Unless there's a guarantee that the
push/pull mechanism will be round-robin scheduled (which as I'm reading
the code there isn't), just increasing the deficit on every call to
reorder_txq() is not going to ensure fairness (it'll probably help
some,
but it won't be completely fair).
However, if we add the check to reorder_txq() so the deficit increase +
rotation is only done if the TXQ is at the head of the list, we'll get
round-robin-equivalent behaviour since a TXQ will only get to continue
when it happens to have rotated to the head of the queue. As I
mentioned
previously it will break MIMO, but I we could fix that later once we've
verified that the basic mechanism works.
Hmm... The pull mechanism operates in round-robin fashion. Agree that
accessing only head node is right way of ensuring fairness. Will fix it
and rename as ieee80211_txq_can_transmit().
Thanks Toke for your feedback.
-Rajkumar
