packet drop with intel gigabit / marwell gigabit

OxY oxy at
Fri Mar 24 13:12:05 UTC 2006

hi guys!

well, i changed my motherboard and CPU  from the
asus a7v8x+amd 2000+ xp to 
the abit be7 + p4 2.4 (533fsb)  and the packet loss fell down from 8% to 2%, but
still have loss...
loss coming when i have load.. i guess it decreased because of the bigger resources.
still waiting for tipps, hints, everything :)

  ----- Original Message ----- 
  From: Jin Guojun [VFFS] 
  To: Arne Woerner 
  Cc: Gary Thorpe ; freebsd-performance at ; oxy at 
  Sent: Wednesday, March 22, 2006 6:23 PM
  Subject: Re: packet drop with intel gigabit / marwell gigabit

  Arne Woerner wrote: 
--- "Jin Guojun [VFFS]" <g_jin at> wrote:
In you example:
  Now your 1.6 GB/s reduced to 16MB/s or even worse just based
on this factor.

    What did we show by this <<dd if=/dev/zero ...>> test? I thought
that would prove the memory bandwidth is about 8Gbit/sec
(1GByte/sec; 2 * <dd's bytes/sec number>/2^30).
  It depends on how you use /dev/zero. 

  dd of=/dev/null if=/dev/zero bs=4k count=100k
  tests cache speed

  dd of=/dev/null if=/dev/zero bs=4m count=100
  tests memory bandwidth if your cache is less than 2 MB

  Now you may give me the real memory bandwidth on your system :-)
  I would expect something around 500.
  Notice that your memory copy speed  will  be one half of it. 

  /dev/null device really does nothing beside throwing away data.
  That is, it can be counted as a cost for system call.


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