On Mon, Feb 8, 2016 at 4:34 PM, Felix Fietkau <nbd@xxxxxxxxxxx> wrote: > On 2016-02-08 10:54, Krishna Chaitanya wrote: >> On Mon, Feb 8, 2016 at 2:56 PM, Emmanuel Grumbach <egrumbach@xxxxxxxxx> wrote: >>> On Mon, Feb 8, 2016 at 10:38 AM, Felix Fietkau <nbd@xxxxxxxxxxx> wrote: >>>> Requires software tx queueing support. frag_list support (for zero-copy) >>>> is optional. >>>> >>>> Signed-off-by: Felix Fietkau <nbd@xxxxxxxxxxx> >>>> --- >>> >>> >>> Ok - looks fine, but... and here comes the hard stuff. >>> The frame size in the PLCP is limited in a way that you can't - from a >>> spec POV - enable A-MSDU for low rates. Of course, you don't want to >>> do that for low rates at all regardless of the spec. >>> Since you build the A-MSDU in the mac80211 Tx queue which is not aware >>> of the link quality, how do we prevent A-MSDU if the rate is low / >>> dropping. >>> I'd even argue that when the rates get lower, you'll have more >>> packets piling up in the software queue and ... even more chance to >>> get A-MSDU in the exact case where you really want to avoid it? >> >> Similar to triggering AMPDU setup, we should put this control >> in RC (minstrel) to start/stop AMSDU based on link quality/if the rates >> drop below a pre-defined MCS (or) only for best-throughput rates. > I think starting/stopping A-MSDU based on the rate is a bad idea. > Even with low rates, using A-MSDU can be a good thing (especially for > TCP ACKs), it just needs different size limits. By low rates, i was referring to bad channel conditions (more retries/crc errors) so using AMSDU might trigger more TCP level retries and for case of TCP ACK's its still worse in that it triggers TCP data retires from the peer. -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
