From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <47C0819E.8040000@domain.hid> Date: Sat, 23 Feb 2008 21:27:10 +0100 From: Wolfgang Grandegger MIME-Version: 1.0 References: <47BF446E.50300@domain.hid> <47C02848.70604@domain.hid> In-Reply-To: <47C02848.70604@domain.hid> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-help] gpioirqbench: measuring external interrupt latencies List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Jan Kiszka Cc: xenomai-help Jan Kiszka wrote: > Wolfgang Grandegger wrote: >> Hello, >> >> I'm proud to announce "gpioirqbench", a benchmark tool to measure >> external interrupt latencies. It is derived from Jan's irqbench [1] for >> the PC. Instead of using the serial or parallel port, it uses GPIO pins >> on embedded systems. It measures the time between the generation of an >> interrupt triggered by a GPIO pin and the reply by either the interrupt >> service routine, a kernel-space task or a user-space task. As reply, >> another GPIO pin will be toggled. The setup consists of two systems, the >> log host and the test target. The log host triggers the interrupt on the >> test target and measures the latency. This benchmark is primarily for >> Xenomai/RTDM, but it can also be used for plain Linux or even Linux-rt >> (with the real-time preemption patch). > > Nice stuff! Still I have a few conceptual questions: :-> I did expect them ;-). > 1. Why do you need a Xenomai measurement host? On first glance, you are > just spinning on the reply for the RT target. Why not use plain Linux > for this to increase portability? Most beautiful would be a pure > userspace approach like for irqbench. What prevents this here? Well, I'm not a hardware expert and therefore it was not obvious to me how to connect GPIO pins to the standard PC. To avoid electrical incompatibilities, I chose my good old TQM855L module as log host. I agree, that this solution is rather special and that the one for irqbench would be much better. Any ideas how to interface GPIO pins with the PC? > 2. Do you see a chance to integrate the target'S GPIO interface into the > exiting irqbench backend? That would make it easy to merge the > Xenomai version into the tree. In the end I preferred to make a separated distribution, as various parts are very hardware specific and the driver can also be built as normal Linux character device driver. Wolfgang.