Comments on: Playing with Realtime with Python

By: BobC

BobC — Fri, 17 Oct 2008 18:01:37 +0000

There’s also the PowerNap extension that provides some advanced RTC capabilities: http://dis-dot-dat.net/index.cgi?item=/code/powernap/

By: Anonymous

Anonymous — Wed, 30 Nov -0001 00:00:00 +0000

I don't understand the structure of your code. I also fail to see where you make use of the Pyrex module. Could you elaborate further?

Alain

By: Jkx

Jkx — Wed, 30 Nov -0001 00:00:00 +0000

The structure is quite simple, just set the right value in /dev/rtc, and after call the read on it. It will block until you receive an interrupt.

The pyrex code, simply implement a switchRTCPriority(nb), that should be call before setting the rtc. (I added this after, so it isn't really clear)

The right code should be:

import os, time

# some linux kernel header
RTC_IRQP_SET = 1074032652
RTC_PIE_ON =  28677
RTC_PIE_OFF = 28678


# get a hight priority
switchRTCPriority(60)

# open the realtime clock
....

By: David Wilson

David Wilson — Wed, 30 Nov -0001 00:00:00 +0000

Have you considered the possibility of using the Linux networking stack to limit your send rate? This would greatly reduce the CPU load induced by your idle loop, and allow the networking stack to cooperatively provide QoS with any other network streams active in the system.

You main loop could then simply become a select() that blocks until your socket is writeable, and everything else is delegated back to the system.

I couldn't even begin to advise you as to how to go about setting up Linux to do this, although I believe TLDP has several HOWTOs on the subject.

HTH,

David.

By: Jkx

Jkx — Wed, 30 Nov -0001 00:00:00 +0000

Hi, David

This is a quite nice way to do of course. But first the idle loop doesn't eat a lot of CPU (This surprise me a lot too, but this stuff is really efficient).

The main issue, is that Linux and QOS is a pure nightmare. I setup several QOS in a past life using some BSD (pf based on netbsd).. and the syntax is clean, and works out of the box. On Linux you have bunch of QOS module, each doing a different stuffs..

On the other side, I think I gonna build a traffic shapper in pure python. I've been to busy right now.. but perhaps a day until I get too old.

Enjoy ;)