On Thu, 2012-09-13 at 09:43 -0400, Cyril Chemparathy wrote: > This patch fixes an apparent bug in the running weighted average calculation > used in the RED algorithm. > > Going by the described formula: > qavg = qavg*(1-W) + backlog*W > => qavg = qavg + (backlog - qavg) * W > > ... with W converted to a pre-calculated shift, this then becomes: > qavg = qavg + (backlog - qavg) >> logW > > ... giving the modified expression introduced by this patch. > > Signed-off-by: John Dowdal <jdow...@ti.com> > --- > include/net/red.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/net/red.h b/include/net/red.h > index ef46058..05960a4 100644 > --- a/include/net/red.h > +++ b/include/net/red.h > @@ -287,7 +287,7 @@ static inline unsigned long > red_calc_qavg_no_idle_time(const struct red_parms *p > * > * --ANK (980924) > */ > - return v->qavg + (backlog - (v->qavg >> p->Wlog)); > + return v->qavg + (backlog - v->qavg) >> p->Wlog; > } > > static inline unsigned long red_calc_qavg(const struct red_parms *p,
This is going to be a FPP (Frequently Posted Patch) Current formulae is fine. Thats because backlog, at start of red_calc_qavg_no_idle_time() is not yet scaled by p->Wlog. v->avg is scaled, but not backlog. Have you tested RED after your patch ? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
