Fast data acquisition
Hello,
I'm designing a solution for high speed data acquisition. The solution will be based on a Pentium class processor running Linux 2.4.x
The data will be acquired over ISA bus using DMA at the rate of 52Mbit per second and then sent over TCP/IP on Ethernet 100MB connecttion to host computer.
I wonder how to design a driver for the data acquistion bord that will minimize data copying.
I have 2 ideas:
1) the application will open the driver and use a sendfile(devicefd, socketfd, ....) call
2) To have the driver DMA data into the kernel buffer and then calling sock_sendpage directly from the driver.
Do i need to implement some special functionality in the driver to realize
1) or a sendfile will work with an fd to any character device as source?
Maybe somebody already implement something similar?
Please CC me the responce
Thanks
Vadim
Quoted 8 lines · Vadim Lebedev
Hello,
I'm designing a solution for high speed data acquisition. The solution will be based on a Pentium class processor running Linux 2.4.x
The data will be acquired over ISA bus using DMA at the rate of 52Mbit per second and then sent over TCP/IP on Ethernet 100MB connecttion to host computer.
You are not serious. the ISA bus cannot transfer data at this rate. You need to use the PCI bus. The ISA bus transfers data at about 1.5 megabytes per second. The GP bus (ISA without any slots, using a bridge), transfers data at up to 3.0 megabytes per second. You can purchase standard PCI interface chips for a dollar or so. You don't need to design your own. You also need a serial EEPROM to load its required info upon power-up. This is all standard, inexpensive stuff.
Search 'PCI bus interface' on your Web-Crawler.
http://www.interfacebus.com/Design_Connector_PCI.html documents some 'cores' and interface chips.
Quoted 5 lines
I wonder how to design a driver for the data acquistion bord that will minimize data copying.
I have 2 ideas:
Data gets copied very quickly on 400 MHz or greater Pentium-Class machines (about 1,500 megabytes per second). This should not be your concern.
Quoted 2 lines
1) the application will open the driver and use a
sendfile(devicefd, socketfd, ....)call
This works if you correctly implement read() in your driver.
Quoted 4 lines
2) To have the driver DMA data into the kernel buffer and then calling
sock_sendpagedirectly from the driver.
If the hardware can do Bus Mastering, by all means use it. You need to use a TCP/IP "connection" to guarantee that the receiver gets your data. Using a piece of kernel code may send a packet, but there's a lot more to networking than that.
Quoted 4 lines
Do i need to implement some special functionality in the driver to realize
1) or a sendfile will work with an fd to any character device as source?
If the driver properly impliments read(). It should work with sendfile.
Cheers,
Dick Johnson
Penguin : Linux version 2.4.18 on an i686 machine (797.90 BogoMips). The US military has given us many words, FUBAR, SNAFU, now ENRON. Yes, top management were graduates of West Point and Annapolis.