From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <47F34C0D.6090809@domain.hid> Date: Wed, 02 Apr 2008 11:04:13 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <20080402012645.506e53ef.Cornelius.Koepp@domain.hid> In-Reply-To: <20080402012645.506e53ef.Cornelius.Koepp@domain.hid> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig02F675164243A57E6BEA8982" Sender: jan.kiszka@domain.hid Subject: Re: [Xenomai-core] latencys drifting into negative (Xenomai 2.4.2/2.4.3) List-Id: "Xenomai life and development \(bug reports, patches, discussions\)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: =?ISO-8859-1?Q?Cornelius_K=F6pp?= Cc: xenomai-core This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig02F675164243A57E6BEA8982 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable Cornelius K=F6pp wrote: > Hello, > I run the latency test from testsuite on several hard and software conf= igurations. Running on Xenomai 2.4.2, Linux 2.6.24 the results shows a "s= trange" behavior: In Kernel mode (-t1) the latencys constantly linear dec= rease. See attached plot 'drifting_latencys_in_kernelmode.png' of latency= test running 48h on Pentium3 700. This effect could be reproduced, even = on other hardware (Pentium-M 1400). As our P3 boards did not support APIC-based timing (IIRC), your kernel=20 has correctly disabled the related kernel support. But the Pentium M=20 should be fine. So could you check if we are seeing some TSC clocks vs.=20 PIT timer rounding issue by enabling the local APIC on the Pentium M? > The usermode (-t0) did not show a drifting, but is influenced by a test= ran in kernelmode before. What do you mean with "is influenced"? >=20 > I talked with Sebastian Smolorz about this and he builds his own indepe= ndent kernel-config to check. He got the same drifting-effect with Xenoma= i 2.4.2 and Xenomai 2.4.3 running latency over several hours. His kernel-= config ist attached as 'config-2.6.24-xenomai-2.4.3__ssm'. >=20 > Our kernel-configs are both based on a config used with Xenomai 2.3.4 a= nd Linux 2.6.20.15 without any drifting effects. 2.3.x did not incorporate the new TSC-to-ns conversion. Maybe it is not=20 a PIC vs. APIC thing, but rather a rounding problem of larger TSC values = (that naturally show up when the system runs for a longer time). Jan --------------enig02F675164243A57E6BEA8982 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 iD8DBQFH80wTniDOoMHTA+kRAmYkAJ0dAMz9mxsYfmCfiRk5AWFjb4gEGgCfcgMl wnpaECZQmbD598ZRPTICz80= =BgTS -----END PGP SIGNATURE----- --------------enig02F675164243A57E6BEA8982--