packet drop with intel gigabit / marwell gigabit

Jin Guojun (VFFS) g_jin at
Sun Mar 19 10:45:41 UTC 2006

OxY wrote:

> CPU utilization is 0% if apache is not running and 10-20%, when 
> running and
> serving 30-40 concurrent downloads (traffic is 3-4MB/s on fxp0 interface)

Is the number 3-4MB/s for  per stream or the total for all 30-40 streams?
Are these downloads sent to a disk?

> i measured the network performance with 'iperf' util, started the 
> server on my box
> and benchmarked with a client on the other gigabit machine.
> it showed 0% packet drop, when apache was not running and 4-7%, when 
> running..
> then i checked how it behave when i shut down apache and init a local 
> file copy from one
> (not system!) disk to other (not system disk either). packet drop was 
> 5-10%, due to the higher load.
> so i think interrupts or just the load takes the network performance, 
> but i have no clue how to fix it.
> is it possible that the 2000+ xp amd is just weak to serve such a 
> traffic? (em0 traffic's maximum is 18-23MB/s)
> i think it might be around 30MB/s without packet drop.

First let's clear the notation -- Is 30MB/s (MBytes/s) = 240Mb/s 
(Mbit/s)  or MB/s means Mbits/s
If  MB/s is MBytes/s and you also write this amount data to a disk, plus 
other traffic on fxp0 to disk too,
then your problem may be bonded by memory bandwidth because CPU 
utilization is low:
    (240 + 24~32) x 2 is about 535 Mbit/s (some chipset/motherboard has 
low memory BW for AMD)
If this is true, then this no thing you can tune. What does the chipset 
(Motherboard) this machine have?

> I did FTP measurement, because what i want is to copy files with high 
> speed from the
> other gigabit machine. However FTP needs resources (CPU, I/O, etc), 
> but iperf not!
> iperf shows 20% CPU utilization when apache not running and when 
> there's no packet drop.
> ps: Now apache says: 14 requests currently being processed
> traffic is 1MB/s on fxp0, and em0 benchmark with iperf says (64k udp 
> window size):
> [  3]  0.0-10.0 sec    235 MBytes    197 Mbits/sec
> [  3] Sent 167375 datagrams
> [  3] Server Report:
> [  3]  0.0-10.0 sec    229 MBytes    192 Mbits/sec  0.066 ms 
> 4115/167375 (2.5%)
> the other gigabit machine is OK, because i have 0% packet drop, when 
> my machine is totally idle.

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