netdev - Re: Strange packet drops with heavy firewalling

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Date:	Thu, 15 Apr 2010 15:23:50 +0200
From:	Benny Amorsen <benny+usenet@...rsen.dk>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Changli Gao <xiaosuo@...il.com>,
	zhigang gong <zhigang.gong@...il.com>, netdev@...r.kernel.org
Subject: Re: Strange packet drops with heavy firewalling

Benny Amorsen <benny+usenet@...rsen.dk> writes:

> I'll keep monitoring the server, and if it starts dropping packets again
> or load increases I'll check whether irqbalanced does the right thing,
> and if not I'll implement your suggestion.

It did start dropping packets (although very few, a few packets dropped
at once perhaps every ten minutes). Irqbalanced didn't move the
interrupts.

Doing

echo 01 >/proc/irq/99/smp_affinity
echo 02 >/proc/irq/100/smp_affinity
echo 04 >/proc/irq/101/smp_affinity

and so on like Erik Dumazet suggested seems to have helped, but not
entirely solved the problem.

The problem now manifests itself this way in ethtool -S:
     rx_no_buffer_count: 270
     rx_queue_drop_packet_count: 270

I can't be sure that I'm not just getting hit by a 1Gbps traffic spike,
of course, but it is a bit strange that a machine which can do 200Mbps
at 92% idle can't handle subsecond peaks close to 1Gbps...

I wish ifstat could report errors so I could see what the traffic rate
was when the problem occurred...

/Benny
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