packet drop with intel gigabit / marwell gigabit

OxY oxy at
Mon Mar 20 10:22:18 UTC 2006

----- Original Message ----- 
From: "Jin Guojun [VFFS]" <g_jin at>
To: "OxY" <oxy at>
Cc: <freebsd-performance at>
Sent: Monday, March 20, 2006 4:05 AM
Subject: Re: packet drop with intel gigabit / marwell gigabit

> OxY wrote:
>> ----- Original Message ----- From: "Jin Guojun (VFFS)" <g_jin at>
>> To: "OxY" <oxy at>
>> Cc: "Chuck Swiger" <cswiger at>; <freebsd-performance at>
>> Sent: Sunday, March 19, 2006 11:46 AM
>> Subject: Re: packet drop with intel gigabit / marwell gigabit
>>> 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?
>> it's a total, 30-40 streams get the files from two sata disks in raid1
>>> ....
>>> 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?
>> 30MB/s is Megabytes/sec, currently i have 18-20MB/s peak and 15MB/s avg.
>> it's not 535Mbit/s, because i only download it to my machine, no upload.
>> disks are different from apache disks, these disks have own controller in 
>> one pci slot.
>> the packet drop is 5-7% at 200Mbit iperf test, 100Mbit drop is around 
>> zero.
>> i have <ASUS A7V8X> on motherboard which has VIA KT400 northbridge
> Yes, this is one of problem chipset. I bought one about 3 years ago.
> After one day testing, I returned it for changing a A7V600 (VIA KT600 
> chipset),
> which is 30% more memory bandwidth than KT400. A7V600 can only receive max
> 604 Mb/s TCP, so You can imagine what the KT400 can do :-)
> I do not have a record (because it is too bad), but taking minimum 25% 
> off,
> it probably about 420-430 Mb/s (50MB/s). Now you can do the math when the
> machine also writing data to a disk (assume disk a fast enough). I would 
> expect
> 2/3 of 430 Mb/s, which is about 280~290 Mb/s (35 MB/s).
> If you experiment these numbers, you are at there. No improvement you can 
> make
> further.

i have doubts, because when i have 3-4MB/s traffic on fxp0 then em0 peak
is 18MB/s, but when fxp0 is almost idle, have 500kB/s traffic, then em0 can 
do 20MB/s..

> AMD is good. As I mentioned earlier, it is motherboard shipset make's 
> problem.
> I like AMD CPU, and I amd writing from A7V600 with AMD XP 2100+ :-)
> The ABIT motherboard has an Intel 845 chipset, which has very good memory 
> bandwidth.
> You should be able to saturate your GigE interface on this motherboard.
> If you have problem to obtain the performance, we can tune it .
> Good luck!

okay, i check with intel soon :)
>    -Jin

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