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<hr><p align="left"><small>发信人: plato (纯真年代), 信区: Embedded <br>
标 题: linux for ppc chapter 15 <br>
发信站: BBS 水木清华站 (Wed May 30 23:21:04 2001) <br>
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15. Real Time Response <br>
Check out MontaVista's Linux Real-Time characterisation projects at http://w <br>
ww.mvista.com/realtime <br>
15.1 Soft <br>
For many applications a soft real time user space thread is adequate, partic <br>
ularly if you minimise kernel scheduling latency with the patches at: http:/ <br>
/www.redhat.com/~mingo/lowlatency-patches/ <br>
Also, see: http://lists.linuxppc.org/listarcs/linuxppc-embedded/199912/msg00 <br>
006.html <br>
15.2 Hard <br>
If your application requires a hard real time response with guaranteed low l <br>
atency, you may need to encapsulate the real time aspects in a device driver <br>
. This is how devices which have real time constraints such as serial ports <br>
and disk drives are traditionally handled under most non-realtime operating <br>
systems, including Linux. <br>
Interrupt Latency <br>
The real-time response of a driver will still be affected by other kernel co <br>
de which may disable interrupts for unknown periods, increasing effective in <br>
terrupt latency. For some tools to help measure interrupt latency, see: http <br>
://www.drfruitcake.com/linux/irq_blk.html <br>
RTLinux - Real Time Linux <br>
http://www.rtlinux.com/ <br>
If you need better latency guarantees than offerred by the kernel, use Real <br>
Time Linux to decouple the hard real time portion from the rest of your appl <br>
ication. v3.0 includes support for PowerPC. <br>
Also, search for RTLinux. <br>
RTAI - Real Time Application Interface <br>
http://www.aero.polimi.it/projects/rtai/ <br>
The Real Time Application Interface is a kernel module which uses a hardware <br>
abstraction layer to add typical features from an industrial real time oper <br>
ating system to Linux. It consists basically of an interrupt dispatcher and <br>
mainly traps the peripherals interrupts and if necessary re-routes them to L <br>
inux. <br>
RTAI is supported on a number of MPC8xx systems by people like Denx. <br>
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