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[ath] modify cabq and per-node packet usage limits.

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* limit cabq to 64 - in practice if this stays at ath_txbuf then
  all buffers can be tied up by a very busy broadcast domain (eg ARP
  storm, way too much MDNS/NETBIOS).  It's been like this in the
  freebsd-wifi-build AP project for the longest time.

* Now that I figured out the hilarity inherent in aggregate forming
  and AR9380 EDMA work, change the per-node to 64 frames by default.
  I'll do some more work to shorten the queue latency introduced when
  doing data so TCP isn't so terrible, but it's now no longer /always/
  tens of milliseconds of extra latency  when doing active iperf tests.

Notes:

The reason for the extra latency is partly tx/rx taskqueue handling and
scheduling, and partly due to a lack of airtime/QoS awareness of per-node
traffic.  Ideally we'd have different limits/priorities on the QoS/TID
levels per node so say, voice/video data got a better share of buffer
allocations over best effort/bulk data, but we currently don't implement
that.  It's not /hard/ to do, I just need to do it.

Tested:

* AR9380 (STA), AR9580 (hostap) - both with the relevant changes.
  TCP is now at around 180mbit with rate control and RTS protection
  enabled.  UDP stays at 355mbit at MCS23, no HT protection.
This commit is contained in:
Adrian Chadd 2017-01-23 04:47:38 +00:00
parent 57af292d36
commit 5e2c0d2d47
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=312662
1 changed files with 11 additions and 8 deletions
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19
sys/dev/ath/if_ath.c
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@ -1028,12 +1028,16 @@ ath_attach(u_int16_t devid, struct ath_softc *sc)
* otherwise) to be transmitted.
*/
sc->sc_txq_data_minfree = 10;
/*
* Leave this as default to maintain legacy behaviour.
* Shortening the cabq/mcastq may end up causing some
* undesirable behaviour.
* Shorten this to 64 packets, or 1/4 ath_txbuf, whichever
* is smaller.
*
* Anything bigger can potentially see the cabq consume
* almost all buffers, starving everything else, only to
* see most fail to transmit in the given beacon interval.
*/
sc->sc_txq_mcastq_maxdepth = ath_txbuf;
sc->sc_txq_mcastq_maxdepth = MIN(64, ath_txbuf / 4);
/*
* How deep can the node software TX queue get whilst it's asleep.
@ -1041,11 +1045,10 @@ ath_attach(u_int16_t devid, struct ath_softc *sc)
sc->sc_txq_node_psq_maxdepth = 16;
/*
* Default the maximum queue depth for a given node
* to 1/4'th the TX buffers, or 64, whichever
* is larger.
* Default the maximum queue to to 1/4'th the TX buffers, or
* 64, whichever is smaller.
*/
sc->sc_txq_node_maxdepth = MAX(64, ath_txbuf / 4);
sc->sc_txq_node_maxdepth = MIN(64, ath_txbuf / 4);
/* Enable CABQ by default */
sc->sc_cabq_enable = 1;