From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <52CC8A18.2020807@xenomai.org> Date: Wed, 08 Jan 2014 00:13:28 +0100 From: Gilles Chanteperdrix MIME-Version: 1.0 References: <44lhyrmuw9.fsf@be-well.ilk.org> <52CC7D71.4040703@steinkuehler.net> <52CC83F1.40000@xenomai.org> <52CC85C5.4060703@steinkuehler.net> In-Reply-To: <52CC85C5.4060703@steinkuehler.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai] Altera Cyclone V List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Charles Steinkuehler Cc: xenomai@xenomai.org -----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On 01/07/2014 11:55 PM, Charles Steinkuehler wrote: > On 1/7/2014 4:47 PM, Gilles Chanteperdrix wrote: >> On 01/07/2014 11:19 PM, Charles Steinkuehler wrote: >>> The single-core A8 on the BeagleBone is good for about 25 uS >>> typical and 80 uS or so worst case latency. >> >> That is really high. On a 720MHz OMAP3, with the latency test >> running with a 100us period, I typically get latencies close to >> 40us (under dohell load). Granted I do not run many >> functionalities of the SOC (typically, not the graphic >> processor), but I would not expect latencies to get so high. Is >> there any chance you could trigger a trace with the I-pipe >> tracer? > > I can try...give me a while to sort through the I-pipe:Tracer wiki > page (or are there better instructions?). Enable I-pipe tracer in kernel configuration, especially IPIPE_TRACE_MCOUNT, and IPIPE_TRACE_VMALLOC. When the system has booted, do: echo 1 > /proc/ipipe/trace/enable echo 1000 > /proc/ipipe/trace/back_trace_points Then launch latency -p 200 -f Run the load you usually run (for instance dohell). When the test is finished, do cat /proc/ipipe/trace/frozen > /tmp/frozen.txt then post the resulting frozen.txt to this list. Expect the latency found by the test to be double the latency you get without the I-pipe tracer. > > This may also have improved somewhat...my numbers are from a year > or so ago when everything first started working. I haven't been > regression testing the latest kernels. I know there have > been significant improvements on both the Xenomai side and with the > BeagleBone kernel patches/drivers. Actually, OMAP3 latency has been around 40us since 2.6.35. 2.6.33 even was at 35us. Note that it is the latency at 10kHz, if you are running with a lower frequency, you will get higher latencies. Also note that there are some options which improve latency, such as: compiling kernel and user-space using thumb2 (but in that case do not forget to enable ARM_ERRATA_430973) optimize for size disable CONFIG_PREEMPT enable stack unwinding disable CONFIG_SMP (obviously, but it may be enabled by default if you are using omap2plus_defconfig, since it also compiles for omap4) disable unlocked context switch (xenomai option) disable root thread priority coupling (xenomai option) - -- Gilles. -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) Comment: Using GnuPG with Icedove - http://www.enigmail.net/ iD8DBQFSzIoYGpcgE6m/fboRAhyRAJ48P6kxKSPh2IeNP0xwwh8cr35KhwCfQo20 cMlOFxFAV7dVNKaPWi6+XW0= =hMP+ -----END PGP SIGNATURE-----