From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <47B14FF9.8010207@domain.hid> Date: Tue, 12 Feb 2008 08:51:21 +0100 From: Jan Kiszka MIME-Version: 1.0 References: <51CAD0CE1504444DBE77CBBE51A0135D376B33@domain.hid> In-Reply-To: <51CAD0CE1504444DBE77CBBE51A0135D376B33@domain.hid> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigBF71DB867E9F4E78081DBDAD" Sender: jan.kiszka@domain.hid Subject: Re: [Xenomai-help] pit List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Steven Seeger Cc: xenomai@xenomai.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigBF71DB867E9F4E78081DBDAD Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Steven Seeger wrote: > I compiled the kernel for 586 and am running the PIT timer. I still get= > the 17000-18000 context switches per second, and now the irq0 handler i= s > taking up 11% of the CPU instead of only 5% when the two 8000Hz tasks > are loaded but delayed on events. I think that the problem isn't with > pit, but with the tasks being periodic even though they are blocked.=20 That makes sense: Periodic timers keep on firing. That would explain up=20 to 16000 IRQ invocations per second. And the other 1000-2000 come from=20 Linux? As suggested earlier: you can reduce the number of IRQ events by basing=20 your periodic tasks on the same start date. Then both will be woken up=20 at the same times and their priority will decide about the execution orde= r. >=20 > Running in PIT mode with periodic timing on uses only 9.5% of the CPU. = I > show about 9000 context switches per second. (the 2 8000 hz tasks and > the 1000 hz linux interrupt.) Do you need Linux at 1 KHz? You may even want to try NO_HZ. >=20 > With periodic timing, it's 5.4% when the tasks idle and about 9000 > context switches a second. When one of them becomes active, the irq0 > handler is using 10% of the CPU and the sound task is using about 8%. > These are two kernel tasks. >=20 > =20 >=20 > Userspace stack size is set to 64k. I forgot to mention this to Philipp= e > earlier. >=20 > =20 >=20 > Perhaps the problem is the overhead that the timer handler introduces > being able to support multiple skins with individual timebases. It > sounds like in order to save some cpu cycles, I may want to turn off > periodicity while threads are idle and also avoid setting threads > periodic when they can be driven some other way.=20 I'm still wondering with what older numbers you compare all the nice=20 stats you now generate. Neither older Xenomai nor RTAI provide=20 comparable statistics. Are we doing fair comparisons here? Jan --------------enigBF71DB867E9F4E78081DBDAD 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 iD8DBQFHsU/5niDOoMHTA+kRAn9iAJ4umUzkX7fls5cENiUVFJN5/fpo+ACfZnBj qn8yHJdzCNan1OsyzH/ihoA= =xOJM -----END PGP SIGNATURE----- --------------enigBF71DB867E9F4E78081DBDAD--