From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <443CB06C.2080202@domain.hid> Date: Wed, 12 Apr 2006 09:46:52 +0200 From: Jan Kiszka MIME-Version: 1.0 Subject: Re: [Xenomai-help] question about the latency test running on Blackfin References: <1CFEB358338412458B21FAA0D78FE86D042A2FEE@rennsmail02.eu.thmulti.com> <1144294706.12272.32.camel@domain.hid> <4434BDBD.9060102@domain.hid> <1144412822.21632.10.camel@domain.hid> <44365CFA.1020506@domain.hid> <1144809772.7286.47.camel@domain.hid> In-Reply-To: <1144809772.7286.47.camel@domain.hid> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig9D6E4E6CC4D1DCD4919E177C" 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: Li Yi Cc: xenomai@xenomai.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig9D6E4E6CC4D1DCD4919E177C Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Li Yi wrote: > Hi Philippe, >=20 > According to your answers, I updated the document on Xenomai on > Blackfin: (http://docs.blackfin.uclinux.org/doku.php?id=3Dadeos) with t= he > test result of different modes, setting XENO_OPT_TIMING_SCHEDLAT =3D 1= =2E > But I still have some question about the test result, hoping for your > help: >=20 > When running this test in mode 0, the worst case latency is 65 us, (HSD= | > max| 65 - 66 | 1). This result is get when there is no workload. Can I > say this system is "Hard Real-time" because most of the latency samples= > are in a limited range? =20 Soft RT: the more samples remain under the required limit the higher is the quality of the system Hard RT: ALL samples must be below the limit So, for hard RT, those 65 us is the interesting number. How did you create the system load? Typical tests contain some cache benchmarking tool (I prefer calibrator: http://www.cwi.nl/~manegold/Calibrator) + network load (e.g. ping -f) + hard disk or other persistent storage access (e.g. dd if=3D of=3D/dev/null). How much MHz does your board have, and to what can it be compared when looking at other architectures. 65 us looks quite (too?) good for low-end, but maybe the blackfin isn't actually low-end. >=20 > That is, from the test result: > HSS| min| 59| 31.746| 0.632 > HSS| avg| 599965| 33.365| 2.151 > HSS| max| 59| 53.339| 2.739 >=20 > Can I make the conclusion that the schedule latency is "determinative" = and the system is "hard real-time"? If not, > what is the expected test result? Xenomai is able to provide hard real-= time, right? Yes, Xenomai is a hard-RT system. But this doesn't depend on a specific worst-case latency number, rather on the fact that a hardware-dependent upper limit can be provided that is independent of the (here:) Linux load= =2E Jan --------------enig9D6E4E6CC4D1DCD4919E177C Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFEPLBsniDOoMHTA+kRAvZIAJwM5+zHvBXlcRD85C7DPJu576qZ/gCaAy9R b0zJa0mekAgV4GwV4yWxS4Q= =2gKo -----END PGP SIGNATURE----- --------------enig9D6E4E6CC4D1DCD4919E177C--