Without looking at the board, it's hard to say for sure, but Ethernet is often the
defining performance factor in poorly designed boards. We often observe a 40-50
microsecond
jump that usually breaks down to 15 microseconds for RTL interrupt delay code, and up
to 30
or so microseconds delay as the Ethernet chip does slow DMA of packets over the bus.
RTL does not automatically turn off interrupts when a thread starts, so you can try
doing that by hand to see what happens. Even so, my guess is poor motherboard design
or a configuration problem. A board in which DMA is very slow will behave this way.
We have done things like disable promiscuous mode and fiddle with PCI bus timings on
some boards.
On Wed, Feb 20, 2002 at 06:48:07AM +0000, [EMAIL PROTECTED] wrote:
>
>
>
> If the IRQ is delayed, I don't understand the following situation
> with a periodic task :
>
> A periodic task is running under RTL3.0-2.2.19 on a Pentium-II board with integrated
> ethernet chip (Intel PRO/100+).
> The task is setup to run every 3ms with a runtime of approx. 300us. As long as there
>is
> no traffic on the network part where the board is attached to, the start time and
>run time of
> the task is stable.
> As soon as the ethernet load on the LAN segment gets more heavy, the start time of
> the task varies around 250us and the run time of the task varies around 100us.
> The traffic on the LAN does not belong to my board, it's a file transfer between
> to other nodes on the network.
> The driver for the ethernet chip is loaded as a linux driver (not a RTL driver).
>
> What can I do to get stable start and run time of the task ?
>
> Do I have to disable the interrupt of the chip while my RT task is running or is
> this done automatically by RT-Linux when my RT task gets active ?
>
>
>
> Oliver
>
> -------- Original Message --------
> Subject: Re: [rtl] RTLinux IRQ handler (19-Feb-2002 18:37)
> From: [EMAIL PROTECTED]
> To: [EMAIL PROTECTED]
>
> > Delayed.
> >
> > On Tue, Feb 19, 2002 at 12:34:46PM -0500, [EMAIL PROTECTED] wrote:
> > > Suppose you have a rtlinux thread running and a hard irq is raised, which
> > > is not handled by rtlinux but by the linux system, is the linux irq handler
> > > activated immediatly, or is it delayed until the linux kernel gets
> > > activated again?
> > >
> > > Thanks in advance
> > >
> > > Damien GUIHAL
> > > Nantes France
> > > --
> > >
> > >
> > >
> > >
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> >
> > --
> > ---------------------------------------------------------
> > Victor Yodaiken
> > Finite State Machine Labs: The RTLinux Company.
> > www.fsmlabs.com www.rtlinux.com
> >
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>
> To: [EMAIL PROTECTED]
> [EMAIL PROTECTED]
> Cc: [EMAIL PROTECTED]
>
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---------------------------------------------------------
Victor Yodaiken
Finite State Machine Labs: The RTLinux Company.
www.fsmlabs.com www.rtlinux.com
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