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Date:      Sat, 05 Oct 2002 17:16:23 -0700
From:      Steve Francis <steve@expertcity.com>
To:        freebsd-questions@freebsd.org
Subject:   Help with net.inet.ip.intr_queue_maxlen
Message-ID:  <3D9F80D7.1010006@expertcity.com>

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Can someone help me with net.inet.ip.intr_queue_maxlen tuning?

Firstly, its the "size of the IP input queue", per the source.

So does that mean after the NIC has received the packet, the interupt
from the NIC has been processed and the packet retrieved from the NIC,
then the packet is placed in this queue, before the IP stack looks at it?
i.e. its unrelated to interupt coalescing or polling, or NIC
performance, as they have already occurred in order to put the packet
into the queue. Yes?

I am getting incrementing net.inet.ip.intr_queue_drops at around 8,000
pps (increasing drops at rate of 10 or so per second.)
Yet, if my statement above about what the queue is, is correct, then it
just means that the system was busy doing stuff before it had a chance
to process the incoming packets, so there was no room for new ones to
enter the queue. But as the system was only 50% busy, then if I increase
the input queue, I should be able to avoid these drops, correct? At
least until the system gets a lot busier.

Is there a sane upper recommended limit to the queue length?

Or am I way off base here?
Thanks


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