From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4905D964.7060805@domain.hid> Date: Mon, 27 Oct 2008 16:08:20 +0100 From: Philippe Gerum MIME-Version: 1.0 References: <1224605536.10407.15.camel@domain.hid> In-Reply-To: <1224605536.10407.15.camel@domain.hid> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai-help] Reducing Kernel Mode Interrupt Latency Reply-To: rpm@xenomai.org List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Henry Bausley Cc: xenomai@xenomai.org Henry Bausley wrote: > Is there any way the kernel mode interrupt handling maximum times can be > decreased. I very much need to reduce my kernel mode interrupt > latencies. I know my hardware is capable of better performance based > upon measurements done with RT Linux. Below is our timing comparison, > all times are the maximums. > > > Xenomai 2.4.5 interrupt handler w/ Kernel 2.6.26 powerpc, gcc 4.2 > ------------------------------------------------------------------- > AMCC 440EP - 24.5 usec > AMCC 460EX - 16.5 usec > While running long performances tests on a Sequoia board here (I'm still investigating the latency trace data and evaluating optimizations), I've never been able to reproduce such worst case latency values. The figures I have on the 440EPx (w/ 2.6.26 + Xenomai 2.4.5 + I-pipe 2.2-07 + ELDK-4.2 toolchain) are: klatency: 15.2 us latency -t2 : 17.1 us latency -t1: 26.1 us latency -t0: 34.9 us /proc/xenomai/latency reset to 0 (no timer shot anticipation) continuous process creation loop and interrupt flood on entry. The figure you are most likely interested in - the one that actually compares with RTLinux's latency test - is given by the klatency test, i.e. pure in-kernel timer handler, no user-space Xenomai thread). Could you tell us a bit more about your kernel config, and the kind of stress you put on the system? TIA, > > FSM Labs RT-Linux 2.2 w/ Kernel 2.6.14 ppc, gcc 3.3 > --------------------------------------------------- > AMCC 440EP - 10.0 usec > AMCC 460EX - Not Available, would require 10's of thousands of dollars > to WindRiver > > > > > _______________________________________________ > Xenomai-help mailing list > Xenomai-help@domain.hid > https://mail.gna.org/listinfo/xenomai-help > -- Philippe.