linux-kernel - Re: bad networking related lag in v2.6.22-rc2

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Date:	Wed, 23 May 2007 21:25:59 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Patrick McHardy <kaber@...sh.net>
Cc:	Ingo Molnar <mingo@...e.hu>, Anant Nitya <kernel@...chanda.info>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"David S. Miller" <davem@...emloft.net>,
	Linux Netdev List <netdev@...r.kernel.org>
Subject: Re: bad networking related lag in v2.6.22-rc2

On Wed, May 23, 2007 at 12:56:04PM +0200, Patrick McHardy wrote:
> 
> Looking at the recent changes to __qdisc_run, this indeed seems
> to be the case, when the qdisc is throttled and has packets queued
> we return a value != 0, causing __qdisc_run to loop until all
> packets have been sent, which may be a long time.

Good catch! I was obviously half awake at the time :)

We could also fix it this way:

[NET_SCHED]: Fix qdisc_restart return value when dequeue is empty

My previous patch that changed the return value of qdisc_restart
incorrectly made the case where dequeue returns empty continue
processing packets.

This patch is based on diagnosis and fix by Patrick McHardy.

Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>

Thanks,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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--
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index f28bb2d..cbefe22 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -169,8 +169,8 @@ requeue:
 		else
 			q->ops->requeue(skb, q);
 		netif_schedule(dev);
-		return 0;
 	}
+	return 0;
 
 out:
 	BUG_ON((int) q->q.qlen < 0);
-
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