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Date: Thu, 13 Sep 2012 09:43:40 -0400 From: Cyril Chemparathy <cyril@...com> To: <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org> CC: <davem@...emloft.net>, <david.ward@...mit.edu>, <eric.dumazet@...il.com>, <jdowdal@...com>, <paul.gortmaker@...driver.com>, Cyril Chemparathy <cyril@...com> Subject: [PATCH] sch_red: fix weighted average calculation 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 <jdowdal@...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, -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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