[Winpcap-users] packet lost at 480Mbps

[Gianluca Varenni]

  ----- Original Message ----- 
  From: jli at altobeam.com 
  To: winpcap-users at winpcap.org 
  Sent: Sunday, March 15, 2009 8:39 PM
  Subject: [Winpcap-users] packet lost at 480Mbps




  Hi guys:
   Last mail has some format problems,and  i'm sorry for that .
   I use wireshark to capture data at 480Mbps and found packets lost when wireshark indicate that "Drop" is zero and "Receive but no buffer" is not zero. 
  So I learned the sourcecode of wireshark and winpcap, found that "Receive but no buffer" in wireshark come from PacketRequest() in packet32.dll using DeviceIoControl() and the function code is "OID_GEN_RCV_NO_BUFFER", which MSDN explains as follows:

  As a query, the OID_GEN_RCV_NO_BUFFER OID specifies the number of frames that the NIC cannot receive due to lack of NIC receive buffer space. Some
  NICs do not provide the exact number of missed frames; they provide only the number of times at least one frame is missed.

  Is that means my NIC hardware buffer is too small?

Yeah. Actually "Receive buffer space" is a generic term. Most probably the DMA receive buffers (that are in the RAM of your PC) are not big enough, or the PCI/PCIe/USB bus on which the NIC is installed is not fast enough to transfer all the data from the device to the host.

  Can i improve reading speed by recompiling npf.sys to fix this problem?

No

  If i use packet.lib, what should i do to make read operation more fast besides decrease value of mintocopy ?

Decreasing the mintocopy can actually impact the perfomance in the opposite way: if mintocopy is low, the number of user/kernel transitions (i.e. system calls) to move packets from kernel mode to user mode gets higher and can impact the CPU load on the system.

Have a nice day
GV

  Here are some information of my laptop: WinXp sp3, NDIS5.1, dual CPU at 2GHz, 2G memory, Realtek RTL8168C(P)/8111C(P) PCI-E Gagibit Ethernet NIC



------------------------------------------------------------------------------


  _______________________________________________
  Winpcap-users mailing list
  Winpcap-users at winpcap.org
  https://www.winpcap.org/mailman/listinfo/winpcap-users
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.winpcap.org/pipermail/winpcap-users/attachments/20090316/51f3907a/attachment.htm