Re: Question regarding minstrel(_ht) and retry limits

[Felix Fietkau <nbd@openwrt.org>]

On 2013-03-07 4:31 PM, Simon Wunderlich wrote:
> Hello list,
> 
> as you might be aware, it is possible to set short and long retry limits
> to specify how often a frame should be retransmitted before getting dropped.
> 
> However, it appears that minstrel completely ignores any retry limit, and it is
> also not applied later in the code path. I've hacked minstrel_ht a little bit
> to apply the retry limits in minstrel_get_rate() before returning the rates
> (i.e. just cutting retries at the end from the struct ieee80211_tx_rate array).
> 
> This worked for me, but is probably not clean either and might disturb minstrel
> operation. Also minstrel uses much more retries than default retry limits
> (short: 7, long: 4), so this patch might introduce behaviour changes.
> 
> What is your opinion on this? Can we get it properly supported? Does it hurt
> to just use the first $retry_limit retries, and cut the rest at other rates
> at the end?
I think simply cutting off from the end of the retry chain is a bad idea
- if there are too many scheduled retries in the max throughput rate, it
will not make it to the fallback to a reliable rate if that fails. A
better approach is to make minstrel use fewer retries per rate.

- Felix