Re: [Madwifi-devel] Throughput reduction

[Scott R. <sco...@gm...>]

Hi Derek,

On 1/04/2009, at 2:16 PM, Derek Smithies wrote:

> ...
>
> and the change in question was:
>
> --- ath/if_ath.c        (revision 3755)
> +++ ath/if_ath.c        (revision 3756)
> @@ -7188,8 +7180,6 @@
>  static int
>  ath_txq_update(struct ath_softc *sc, struct ath_txq *txq, int ac)
>  {
> -#define        ATH_EXPONENT_TO_VALUE(v)        ((1<<v)-1)
> -#define        ATH_TXOP_TO_US(v)               (v<<5)
>         struct ieee80211com *ic = &sc->sc_ic;
>         struct wmeParams *wmep =
> &ic->ic_wme.wme_chanParams.cap_wmeParams[ac];
>         struct ath_hal *ah = sc->sc_ah;
> @@ -7197,9 +7187,9 @@
>
>         ath_hal_gettxqueueprops(ah, txq->axq_qnum, &qi);
>         qi.tqi_aifs = wmep->wmep_aifsn;
> -       qi.tqi_cwmin = ATH_EXPONENT_TO_VALUE(wmep->wmep_logcwmin);
> -       qi.tqi_cwmax = ATH_EXPONENT_TO_VALUE(wmep->wmep_logcwmax);
> -       qi.tqi_burstTime = ATH_TXOP_TO_US(wmep->wmep_txopLimit);
> +       qi.tqi_cwmin = (1 << wmep->wmep_logcwmin) - 1;
> +       qi.tqi_cwmax = (1 << wmep->wmep_logcwmax) - 1;
> +       qi.tqi_burstTime = wmep->wmep_txopLimit / 32; /* 32 us  
> units. */
>
>         if (!ath_hal_settxqueueprops(ah, txq->axq_qnum, &qi)) {
>                 EPRINTF(sc, "Unable to update hardware queue "
>
> The bursttime in the 3755 build is wmep->wmep_txopLimit<<5
> The bursttime in the 3756 build is wmep->wmep_txopLimit/32
>
> Now, give the commit the benefit of the doubt.. But I think the  
> commit is
> wrong. Any comment?
>

It looks like a typo. "wmep->wmep_txopLimit << 5" should have become  
"* 32", not "/ 32".

Nice catch :)

--
Scott Raynel
WAND Network Research Group
Department of Computer Science
University of Waikato
New Zealand