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:* [email protected] <mailto:[email protected]>
*Sent:* Sunday, September 26, 2010 10:49 PM
*To:* [email protected] <mailto:[email protected]>
*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" <[email protected]>*
发件人: [email protected]
2010-09-21 07:41
请答复 给
[email protected]
收件人
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主题
Re: [Winpcap-users] About the packets loss , what is the
bottleneck ?
*From:* _yulou liu_ <mailto:[email protected]>
*Sent:* Sunday, September 19, 2010 12:50 AM
*To:* [email protected]_ <mailto:[email protected]>
*Subject:* [Winpcap-users] About the packets loss , what is the
bottleneck ?
There is still the question about packets loss.
 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, Â
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
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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