Rafi Gordon wrote:
Hello,
Thanks.
You said
If you really meant 1 microsecond (as opposed to 1 millisecond)
Yes ,I mean it. In short: it's for a video-audio app; this app can be
termed soft (or semi) real time; The terminology is not important at
all. The fact is that there are scenarios when
the timing is critical; I mean a packet that arrived at a certain time
should not be sent immediately but after some sleep interval; this
if for keeping a specified rate , which is important for a good quality.
So sometimes a microsec sleep is needed, sometimes 5 or more.
(Maybe it would have been better to phrase my question as
sleeping in a resolution of microsecond instead of 1 microsec).
Since you mention packets and I assume you mean network I seriously
doubt that your time limits are anyone near the microsecond ranges.
I might be wrong though (if you're talking about some RF packet and not
Ethernet) , and if so then be aware writing this as a user space
application in Linux is a no go:
Average premption latency on a x86 platform is somewhere near 10
microseconds. The worst case interrupt latency of same is < 2
microseconds but the worst case is ~40 microseconds. This is *after* all
the relevant preemtive kernel patches, lock break and so on has beebn
appllied. [1]
If you cannot miss a bit and you're working in sub 5 micro area and you
wish to use Linux you need to use some sort of an interrupt pipline -
RTAI/Adeos is my personal recomendation.
[1] A little old but gives a good view, espeically since 2.6 is worse,
niot better then 2.4 + patches in this regard:
http://www.linuxforum.dk/2002/program/udstiller/montavista/slides/MontaVista_Real_Time_Linux_CPH_March2.pdf
may I ask ehat is the recommnded way to write a a busy wait loop?
If I am not wrong there is no "noop" command in "C" ; is there a noop
is asm to achieve this ? or simply a loop which just do dummy
operation
like incrementing some integer ?
arch/i386/lib/delay.c in your nearest kernel 2.6 source.
Cheers,
Gilad
--
Gilad Ben-Yossef <[EMAIL PROTECTED]>
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