Emmanuel,
The 10
ms is a product of the HZ value that has been defined in one of the linux header
files. I can't remember which one but it has been called out here on the
mailing list several times. This is the value that sets up the minimum
task switching frequency. People have changed this value from 100 to 1000
in order to provide faster context switching times to solve that exact problem
with 10 ms. This can reduce overall performance a little because of the
overhead involved in the context switch. However, some people have been
happy with this method.
On
another note it can be said, as it has so many times on this mailing list, that
the internet is NOT hard real-time capable. It does not matter what
you do, if you are not on a dedicated network, you will have latencies caused by
other traffic beyond your control. Even rtlinux can not solve that
problem. However, there is a module available called rtnet that can
provide access to the network from rtlinux. It's capabilities are limited
by the network you are using it on.
The
good thing is that rtlinux can solve your task scheduling needs. It can
provide 1 ms scheduling with ease. Just remember, the task must complete
its cycle in less than 1 ms.
I hope
this helps.
Rich
-----Original Message-----
From: Jammeh E A [mailto:[EMAIL PROTECTED]]
Sent: Friday, October 12, 2001 3:24 AM
To: [EMAIL PROTECTED]; Emmanuel Jammeh
Subject: [rtl] Help on real time scheduling
Hello,. I am a research student at the university of essex uk with interest in the transmission of quality video over ip network.
I am presently developing an application for the transmission of real time video over the Internet and i need to be able to generate (send) packets at fixed regular time intervals, wherein lies my problem.
I need to send say a single packet every 1ms, which I cannot do, and it seems that the lowest resoultion i can get from my computer is 10ms.
I tried using the following functions to provide the delay (scheduling)
1: select()
2: usleep()I will be very grateful for any suggestions. Thank you in advance.Anxiously awaiting a response.-- ******************************** * Emmanuel A Jammeh * * Postgrad Research Student * * University of Essex * * Colchester CO4 3SQ * * England * * * * Tel: 00 44 1206 53 7101 * * email: [EMAIL PROTECTED] * * [EMAIL PROTECTED] * ********************************
