[Adeos-main] New I-pipe patch for ARM needs testing.

[Adeos-main] New I-pipe patch for ARM needs testing.

[Gilles Chanteperdrix]

[-- Attachment #1: Type: text/plain, Size: 1500 bytes --]


Hi,

in Xenomai repository (trunk and v2.3.x branch), you will find
adeos-ipipe-2.6.20-arm-1.7-03.patch, the latest version of the I-pipe
patch for ARM. In addition to merging support for two new boards (ixp4xx
and at91sam926x), this patch adds a few important features:
- the at91 patch now applies after the I-pipe patch with no reject ;
- it is now possible for Xenomai to preempt Linux during the mm switch,
which should improve Xenomai scheduling latency significantly;
- Xenomai is now able to access directly I-pipe tsc emulation in
user-space, providing a low overhead timing facility to user-space
applications.

Before including this patch in a new release, and because I could only
test the patch on at91rm9200, we would like people to test the patch on
their hardware and give us feedback about the stability and performance.
In order to adequately stress-test Linux mm context switch, please use
something along the lines of the attached test_switch.c.

As for tsc emulation in user-space, I only implemented it for machines
with a free-running counter, hoping that someone (maybe Sebastian or
Stelian ?) with hardware whose tsc is based on a decrementer could do
the work. This tsc emulation in user-space also required to rework a bit
Xenomai configure script: it is now necessary to pass a
--enable-arm-mach option to configure, and to pass the option
--enable-arm-tsc to enable the tsc.

Thanks in advance.

-- 
                                                 Gilles Chanteperdrix

[-- Attachment #2: test_switch.c --]
[-- Type: text/x-csrc, Size: 237 bytes --]

#include <stdio.h>
#include <stdlib.h>

#include <sys/types.h>
#include <unistd.h>
#include <sched.h>


int main(void)
{
	pid_t child = fork();

	if (child < 0) {
		perror("fork");
		exit(EXIT_FAILURE);
	}

	for (;;)
		sched_yield();
}

Re: [Adeos-main] New I-pipe patch for ARM needs testing.

[Stelian Pop]

Le lundi 04 juin 2007 à 19:39 +0200, Gilles Chanteperdrix a écrit :
> Hi,
> 
> in Xenomai repository (trunk and v2.3.x branch), you will find
> adeos-ipipe-2.6.20-arm-1.7-03.patch, the latest version of the I-pipe
> patch for ARM.

Great job !

[...]

> As for tsc emulation in user-space, I only implemented it for machines
> with a free-running counter, hoping that someone (maybe Sebastian or
> Stelian ?) with hardware whose tsc is based on a decrementer could do
> the work.

I'd take a look, but I lack the hardware right now. I'll probably have
access to the ARM Integrator board in a few weeks, at some time before
the end of July. Unless someone else implements it sooner than that...

Stelian.

-- 
Stelian Pop <stelian@domain.hid>

Re: [Adeos-main] New I-pipe patch for ARM needs testing.

[Sebastian Smolorz]

Stelian Pop wrote:
> Le lundi 04 juin 2007 à 19:39 +0200, Gilles Chanteperdrix a écrit :
> > Hi,
> >
> > in Xenomai repository (trunk and v2.3.x branch), you will find
> > adeos-ipipe-2.6.20-arm-1.7-03.patch, the latest version of the I-pipe
> > patch for ARM.
>
> Great job !
>
> [...]
>
> > As for tsc emulation in user-space, I only implemented it for machines
> > with a free-running counter, hoping that someone (maybe Sebastian or
> > Stelian ?) with hardware whose tsc is based on a decrementer could do
> > the work.
>
> I'd take a look, but I lack the hardware right now. I'll probably have
> access to the ARM Integrator board in a few weeks, at some time before
> the end of July. Unless someone else implements it sooner than that...

I'm also not able to test and extend the patch right now because I'm very busy 
with other work at the moment. So my contribution must wait some weeks, too.

-- 
Sebastian

Re: [Adeos-main] New I-pipe patch for ARM needs testing.

[Sebastian Smolorz]

Hi Gilles,

Gilles Chanteperdrix wrote:
> in Xenomai repository (trunk and v2.3.x branch), you will find
> adeos-ipipe-2.6.20-arm-1.7-03.patch, the latest version of the I-pipe
> patch for ARM. In addition to merging support for two new boards (ixp4xx
> and at91sam926x), this patch adds a few important features:
> - the at91 patch now applies after the I-pipe patch with no reject ;
> - it is now possible for Xenomai to preempt Linux during the mm switch,
> which should improve Xenomai scheduling latency significantly;
> - Xenomai is now able to access directly I-pipe tsc emulation in
> user-space, providing a low overhead timing facility to user-space
> applications.
>
> Before including this patch in a new release, and because I could only
> test the patch on at91rm9200, we would like people to test the patch on
> their hardware and give us feedback about the stability and performance.
> In order to adequately stress-test Linux mm context switch, please use
> something along the lines of the attached test_switch.c.

Finally, I found the time to give adeos-ipipe-2.6.20-arm-1.7-03.patch a try on 
our S3C2440-based board. At first sight, everything runs stable. The latency 
test shows noticeable better results although I didn't run it long enough to 
give a final judgement.

I came across some issues for which I will prepare patches very soon.

--
Sebastian