Opened 7 years ago

Closed 7 years ago

#8683 closed enhancement (wontfix)

minstrel: validity time windows per neighbor

Reported by: isleman Owned by: nbd
Priority: normal Milestone: Backfire 10.03.1
Component: packages Version: Trunk
Keywords: madwifi Cc:


We know that he EWMA calculation is carried out 10 times a second BUT it only happens in presence of unicast traffic so the old EWMA results (computed from the last 100 ms interval) may be quite far in the past if minstrel has remained idle (I'm thinking to mesh environment where traffic is mostly due to olsrd broadcast messages).
I wonder if minstrel could adopt a Validity-Time-Window parameter per neighbor so that a timed-out table is invalidated and forces EWMA mechanism to compute a new rate selection from scratch w/out the expired influences.That's something like a per neighbor reset (currently we can only reset ALL the neighbors tables).
I know that we could get a zero-lenght window by simply setting

static int ath_ewma_level      = 0;

i.e. use only the new results and ignore the old ones but this way we lack some needed minstrel functionalities such as collecting enough success/failure information to be meaningful and minimising the amount of cpu time spent do the updates.

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Change History (2)

comment:1 Changed 7 years ago by jow

  • Owner changed from developers to nbd
  • Status changed from new to assigned

comment:2 Changed 7 years ago by nbd

  • Resolution set to wontfix
  • Status changed from assigned to closed

When I wrote the first mac80211 minstrel implementation, I did experiment with something like this.

I forced the statistics update to reduce the EWMA window if the results were too old. However in the tests that I did with this, not only did it not help at all, it also made rate control behaviour more erratic and jumpy, so I decided to not add any such tweaks.

In the end, old EWMA values are usually closer to reality than zero'd out EWMA values, and I don't think that throwing away old statistics helps with reducing CPU load at all.

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