OxY wrote:
----- Original Message ----- From: "Jin Guojun [VFFS]" <[EMAIL PROTECTED]>
To: "OxY" <[EMAIL PROTECTED]>
Cc: <freebsd-performance@freebsd.org>
Sent: Monday, March 20, 2006 4:05 AM
Subject: Re: packet drop with intel gigabit / marwell gigabit
....
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 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 only
do 20MB/s..
Since you did not get anything better than 35MB/s, then, what is your
doubt --
the maximum I/O A7V8X can do?
The 35 MB/s is the theoretical ceiling based on 2100+ CPU. 2000+ will be
slower.
In previous email, you mentioned you had 240 Mb/s (30 MB/s) on em0 with some
traffic on fxp0, it is pretty much close to your hardware physical
limitation.
Forget drop in this figure, because this demonstrated how much hardware
can do,
rather than lossless transmission.
Once you have determined the ceiling, you need to keep a margin for
lossless Tx.
for other overhead, such as context switch, etc.
20 MB/s is not good enough for this board, you may expect 28-30 MB/s with
fine tuning. Unless you will be happy with 28 MB/s, it does not make
sense to
waste time to try to bump I/O above 30 MB/s for your application if you have
another motherboard.
Again, this motherboard is designed for entertainment boxes not for network
I/O based applications.
-Jin
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