Re: PREEMPT_RT patch vs RTAI/Xenomai

From: Nivedita Singhvi <niv@us.ibm.com>
To: Armin Steinhoff <armin@steinhoff.de>
Cc: rostedt@goodmis.org,
	Asier Tamayo <asier.tamayo@ona-electroerosion.com>,
	linux-rt-users@vger.kernel.org
Subject: Re: PREEMPT_RT patch vs RTAI/Xenomai
Date: Wed, 12 May 2010 18:27:05 -0700	[thread overview]
Message-ID: <4BEB5569.3040008@us.ibm.com> (raw)
In-Reply-To: <4BEAFB7E.90304@steinhoff.de>

Armin Steinhoff wrote:

>> If tuned properly, PREEMPT_RT can easily handle 1ms requirements. On a
>> standard x86 CPU (we support others than x86) our goal is never to be
>>   
> 
> I did a test with user space based CAN driver.
> Already the standard distribution of SUSE 11.2 (non RT) was able to 
> handle 1000 frames per seconds sent by a QNX6 machine !!

If your requirements are "never to exceed" a certain latency,
I highly recommend you run tests for long-durations, rather
than a short period. A 10-min or even a 1 hour run will not
give you a full idea as a 24-72 hour run will.

> The PREEMPT_RT version of SUSE 11.2 is much, much faster :-)
>> over 100us in reaction time.
>>   
> 
> The latency test of PREEMPT_RT shows a latency of ~10us for a dual-core 
> box at 1.8GHz.

Are you using cyclictest? And how long did you run it for?

thanks,
Nivedita