netdev - Re: [PATCH] PATCH 1/2 [SCHED 2.6.24]: Check subqueue status before calling hard_start

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Date:	Tue, 13 Nov 2007 20:41:14 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	peter.p.waskiewicz.jr@...el.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] PATCH 1/2 [SCHED 2.6.24]: Check subqueue status before
 calling hard_start_xmit

From: PJ Waskiewicz <peter.p.waskiewicz.jr@...el.com>
Date: Tue, 13 Nov 2007 09:44:50 -0800

> The only qdiscs that check subqueue state before dequeue'ing are PRIO
> and RR.  The other qdiscs, including the default pfifo_fast qdisc, will
> allow traffic bound for subqueue 0 through to hard_start_xmit.  The check
> for netif_queue_stopped() is done above in pkt_sched.h, so it is
> unnecessary for qdisc_restart().  However, if the underlying driver is
> multiqueue capable, and only sets queue states on subqueues, this will
> allow packets to enter the driver when it's currently unable to process
> packets, resulting in expensive requeues and driver entries.  This patch
> re-adds the check for the subqueue status before calling hard_start_xmit,
> so we can try and avoid the driver entry when the queues are stopped.
> 
> Signed-off-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@...el.com>

Applied, and I'll queue up the other one for -stable, thanks.
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