[Winpcap-users] About the packets loss , what is the bottleneck ?

[Helmut Vaupotitsch]

Hi Gianluca,

1) According to Section 5.3 and Figures 6,9 in 
http://www.winpcap.org/docs/WinPcap-SBAC03.pdf (small packets),
timestamp optimization is switched off in the standard distribution, 
which costs *a lot* of cpu processing.
Is it possible to turn on the "rdtsc" instruction on proper cpu´s? (or 
even turn off driver-timestamping for special purposes)

2) To have a better understanding of the bound NIC and the driver in 
oder to tune the driver settings (e.g. reduce context switches),
it would be very nice to have some informations about:
# usage of kernel buffer (max, average or anything like that)
# no of frames copied to the kernel buffer during one DPC
# no of frames served by one interrupt

3) Regarding performance, what would you prefer,
pcap_next_ex() or pcap_loop()?


Best regards
Helmut


Gianluca Varenni schrieb:
> The copies are the following ones:
>  
> 1. from the NIC driver buffers to the WinPcap kernel buffer (1st copy)
> 2. from the kernel buffer to the user buffer (buffer allocated inside 
> wpcap.dll) (2nd copy)
>  
> If you copy the packets received from pcap_next_ex (or any other pcap 
> receive function) to your own application buffer, that would be a 3rd 
> copy.
>  
> GV
>  
>  
>  
>
> *From:* liu.yulou at zte.com.cn <mailto:liu.yulou at zte.com.cn>
> *Sent:* Sunday, September 26, 2010 10:49 PM
> *To:* winpcap-users at winpcap.org <mailto:winpcap-users at winpcap.org>
> *Subject:* Re: [Winpcap-users] About the packets loss ,what is the 
> bottleneck ?
>
>
> GV> Not at the moment with WinPcap. Having said that, I've used this 
> double copy mechanism to bring several Gbps's to user mode without any 
> packet loss (not with WinPcap, with custom hardware. However the 
> buffering mechanism was the same).
>
> YL> 'double copy mechanism'  ,  Data copy from the user buffer to 
> application(user mode) is the third copy ?  
>
>
>
>
>
> GV>Are you dumping the packets to disk? If so, have you measured the 
> dump-to-disk bandwidth?
>
> YL> Yes,   Dumping packets to disk is my final goal.  But right now , 
>  To avoid the limitation of the disk write speed ,  I just count the 
> packets number in the receive  thread.   But  on the  rate of 614 
> Mbps,   sometimes  there are still packets loss.
>
> PS.     The route of packets transfer is :  FPGA BOARD sends data 
> through ether net -->  PC'S  net card --> winpcap  kernel buffer --> 
> winpcap user buffer  -->  receive thread count .   The FPGA's sending 
> packets rate is about 614 Mbps ,   the size of  each packet is 1460 
> bytes,   every packet has a sequence number  ,   the sending process's 
>  starting and stopping  can be controlled  .    
>
> The app that  I make only counts the packet's number when a packet 
> comes without saving .   While  the  last packet comes ,  the app will 
> compare the number (it counts by itself)  with the sequence number (of 
> the last packet).  Then I will know if there is packets loss.
>
>
>
>
>
>
> *"Gianluca Varenni" <gianluca.varenni at cacetech.com>*
> 发件人:  winpcap-users-bounces at winpcap.org
>
> 2010-09-21 07:41
> 请答复 给
> winpcap-users at winpcap.org
>
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> 收件人
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> 主题
> 	Re: [Winpcap-users] About the packets loss ,        what is the 
> bottleneck ?
>
>
>
> 	
>
>
>
>
>
>  
>
> *From:* _yulou liu_ <mailto:lyulou at gmail.com>
> *Sent:* Sunday, September 19, 2010 12:50 AM
> *To:* _winpcap-users at winpcap.org_ <mailto:winpcap-users at winpcap.org>
> *Subject:* [Winpcap-users] About the packets loss , what is the 
> bottleneck ?
>
>
> There is still the question about packets loss.
> Â Â
> According to the essay  ' Profiling and Optimization of 
> Software-Based Network-Analysis Applications' ,    every packet is 
> copied twice in the main memory before reaching the user.  In order 
> to reduce the cost of CPU and the bus occupying of the SDRAM of pc,  
>  is it possible to copy data directly from the kernel buffer to the 
> final buffer ,  which I want the date kept  in ?  Â
>  
> GV> Not at the moment with WinPcap. Having said that, I've used this 
> double copy mechanism to bring several Gbps's to user mode without any 
> packet loss (not with WinPcap, with custom hardware. However the 
> buffering mechanism was the same).
>
> Â Â
> Here is another idea ---Â Â allocate several different user buffers , 
> once a user buffer is fulled , then let the next user buffer to save 
> the new datas from kernel buffer.  Meanwhile copy datas from the 
> first user buffer to disk (assume that the hard disk write rate is 
> fast enough).  Is this idea work with the winpcap ?Â
>  
> GV>Are you dumping the packets to disk? If so, have you measured the 
> dump-to-disk bandwidth?
>  
> GV
>  
>  
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