packet drop with intel gigabit / marwell gigabit

[Jin Guojun [VFFS]]

OxY wrote:

>
> ----- Original Message ----- From: "Jin Guojun (VFFS)" <g_jin at lbl.gov>
> To: "OxY" <oxy at field.hu>
> Cc: "Chuck Swiger" <cswiger at mac.com>; <freebsd-performance at freebsd.org>
> 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
> http://uk.asus.com/products4.aspx?modelmenu=2&model=226&l1=3&l2=13&l3=62

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 an ABIT BE7 
> (http://www.abit.com.tw/page/uk/motherboard/motherboard_detail.php?pMODEL_NAME=BE7&fMTYPE=Socket%20478&pPRODINFO=Specifications) 
>
> resting somewhere, could it improve the network performance
> with a P4-2.4GHZ(533FSB)?
> (i don't want Intel-AMD flame :) )

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!

    -Jin