netdev - Re: [RFC] niu: RX queues should rotate if budget exhausted

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Message-Id: <20090327.005546.109440539.davem@davemloft.net>
Date:	Fri, 27 Mar 2009 00:55:46 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	dada1@...mosbay.com
Cc:	jesper@...gh.cc, netdev@...r.kernel.org
Subject: Re: [RFC] niu: RX queues should rotate if budget exhausted

From: Eric Dumazet <dada1@...mosbay.com>
Date: Thu, 26 Mar 2009 19:26:20 +0100

> I dont have NIU hardware but it seems this driver could suffer from 
> starvation of high numbered RX queues under flood. I suspect other
> multiqueue drivers might have same problem.
> 
> With a standard budget of 64, we can consume all credit when handling
> first queue(s), and last queues might discard packets.
> 
> Solve this by rotating the starting point, so that we garantee to scan at
> least one new queue at each niu_poll_core() invocation, even under stress.
> 
> Also, change logic calling niu_sync_rx_discard_stats() to take
> into account the device qlen, not bounded by budget (which could be 0)
> 
> Signed-off-by: Eric Dumazet <dada1@...mosbay.com>

This change looks good to me, thanks for spotting this and
suggesting the fix.

It only hits people who don't have usable MSI-X interrupts,
and hey if you have one of these cards what are you doing
sticking it into such a machine :-)

Anyways, I'll apply this directly, thanks a lot!
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