Re: [rtl] use of RT Fifo leads to IRQ be lost RTL 2.2

[Gérard LASSAILLY <g.lassailly@wanadoo.fr>]

Thanks for your reply.

I also think that using shared memory is THE solution to move large block of
data between user space and RT LINUX.

But, I think that the use of RT Fifo should not affect IRQ latency on a Real
Time OS (a can see on my oscilloscope IRQ latency > 1ms !!! when i'm using
rtl_put() with 1,5 Mbytes under RTL2.2 / kernel 2.2.14 / Pentium 266 MMX).

Somebody know if change have been made on RT FIFO code ( RTL 2.2 -> RTL 3.1)
to reduce IRQ latency?

Gérard

----- Original Message -----
From: "Norm Dresner" <ndrez@att.net>
To: <rtl@fsmlabs.com>
Sent: Wednesday, October 31, 2001 2:51 AM
Subject: Re: [rtl] use of RT Fifo leads to IRQ be lost RTL 2.2


> This doesn't seem like a good design to me.  Why can't you
> write the data to shared memory (very fast) and just send a
> pointer through the FIFO telling the user-task where it can
> find the data.
>
>     Norm
>
> ----- Original Message -----
> From: Gérard LASSAILLY
> To: rtl@fsmlabs.com
> Sent: Tuesday, October 30, 2001 4:47 PM
> Subject: [rtl] use of RT Fifo leads to IRQ be lost RTL 2.2
>
>
> I'm using 4 RT Fifo under RT Linux 2.2.
> I write blocs of 1.4 Mbytes in  RT FIFO (1.4 Mbytes by
> rtf_put() ).
> This write in RT Fifo is repeat 25 times by second.
>
> During this, IRQ are lost or delayed.
>
> I don't use RT Fifo in ISR but only to communicate between
> RT task and user task under LINUX.
>
> I think that IRQ are masked during rtf_put() during a long
> time.
>
> Some knowledge please ?
> Do you know if RT Linux 3.0 or 3.1 workaround this
> probleme?
>
> Thanks for your reply.
>
> -- [rtl] ---
> To unsubscribe:
> echo "unsubscribe rtl" | mail majordomo@rtlinux.org OR
> echo "unsubscribe rtl <Your_email>" | mail majordomo@rtlinux.org
> --
> For more information on Real-Time Linux see:
> http://www.rtlinux.org/
>