Message-ID: <3BF8C388.3080200@yahoo.com>
Date: Mon, 19 Nov 2001 16:32:08 +0800
From: Zhongyu <xxx_pku@yahoo.com>
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To: Eckehardt Luhm <bselu@web.de>
CC: linux-kernel@vger.kernel.org
Subject: Re: Network packet drop?
In-Reply-To: <3BF8B2CC.C172F67C@web.de>
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Try to modify the value of max_interrupt_work , like
-static int max_interrupt_work = 20
+static int max_interrupt_work = 200
maybe helpful :-)

Eckehardt Luhm wrote:

>Hello.
>
>I'm studying at the University of Karlsruhe and I'm doing some network
>measurements. In conjunction with network drivers for Linux, I'm
>experiencing very strange effects.
>
>In my setup I have two PCs each with a EEPro-100 network card in it
>connected via an X-link cable. mii-tools says they auto-negotiated a
>speed of 100baseTx-FD. Furthermore I have a program which generates UDP
>packets at the highest possible speed, simply by looping a
>sendto(socket, ...), which should block until a packet is out. What I
>want to measure is the maximum output the network card can do. So I'm
>sending n packets and divide the time needed for that by n.
>
>This works perfectly for larger packets (>500 bytes). All of them are
>being sent out. I'm able to verify this by invoking "ifconfig eth0|grep
>TX" and watch the transmitted packets grow by the number of packets I
>intended to send (in fact it grows a bit more, because of some
>ARP-packets, but that doesn't matter).
>
>But when I set the packet size to say 50 bytes (only data size without
>any headers, so on ethernet this would be 102 bytes), something strange
>is going on. Now not all of the packets I send to the other network card
>are being received. There are leaks of tens of packets at the receiver,
>I'm verifying this with tcpdump. Ok, the receiver was just overtaxed, in
>the syslog I got "eth0: Abnormal interrupt, status 00000002.". So it
>couldn't handle the flood of packets, ok.
>BUT: The sender didn't even send all of the packets! "ifconfig eth0|grep
>TX" grew only about 40-50% of the value it should! e.g. I sent 10.000
>packets, and the TX-counter grew only by 4586, not more. Sometimes I got
>even worse results, especially when decreasing the packet size.
>
>I tried several setups on different PCs, sometimes with X-linked network
>cards, sometimes with a switch between them. None of them worked. Except
>one thing: I tested the same setup described above with other network
>card, two noname products with a realtek 8139 chipset (driver module
>8139too). And you would have guessed it: That worked! The TX-counter
>grew by the correct value, so all packets have been sent out.
>
>And to make the confusion perfect: With forcing the cards to work with
>10 MBit/s-FD (with mii-tool), the same strange "packet drops" as with
>the EEPro-cards appeared.
>
>Is there anybody out there, who can explain what is going on in network
>drivers? What causes these strange effects?
>
>
>Regards, Elu
>--- Eckehardt Luhm, eMail: bselu@web.de
>
>-
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