From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <45D2CE27.5040303@domain.hid> Date: Wed, 14 Feb 2007 09:53:59 +0100 From: Jan Kiszka MIME-Version: 1.0 Subject: Re: [Xenomai-help] CONFIG_PREEMPT & irqbench References: <45D25145.3000407@domain.hid> In-Reply-To: <45D25145.3000407@domain.hid> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig64E1D2B612514E16B17A0891" Sender: jan.kiszka@domain.hid List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus.Franke@domain.hid Cc: Xenomai-help@domain.hid This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig64E1D2B612514E16B17A0891 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Markus Franke wrote: > Dear all, >=20 > I am running some latency tests with irqbench/irqloop. I am wondering > whether it would be possible to achieve better results when activating > CONFIG_PREEMPT and CONFIG_PREEMPT_VOLUNTARILY during the kernel > configuration and running irqloop in User Mode over this kernel? Nope. > Does it make any sense? Nope. :) > I think in theory it should give better results because > this irqloop runs in secondary(linux) domain when started, right? An > increasing preemptibility of the linux kernel should be better for the > irqloop-task. The Linux kernel is already fully preemptible by Xenomai once you applied the I-pipe patch. Therefore, you are free to pick the Linux preemption strategy according to your *Linux* load, independent of what the real-time part needs. Unless you have interactive Linux programs running, I can suggest to pick PREEMPT_VOLUNTARILY or even PREEMPT_NONE, specifically on low-end hardware. > All tests were made under heavy I/O and CPU load by means of "dd", > "pingflood" and "cpuburn". Nevertheless, I can only achieve worse > results when activating CONFIG_PREEMPT. Do you have CONFIG_DEBUG_PREEMPT set as well then? This option still as a small but measurable impact on Xenomai due to micro-dependencies that as scheduled to be removed in the near future. Jan --------------enig64E1D2B612514E16B17A0891 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFF0s4oniDOoMHTA+kRAla7AJ928fCeyr0e3Lz8WLTYVNpsSagljwCePcky 7xZ/7XftLPL7gVcW3MLEk1Y= =uNLS -----END PGP SIGNATURE----- --------------enig64E1D2B612514E16B17A0891--