From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <4BB5B2D3.80708@domain.hid> Date: Fri, 02 Apr 2010 11:03:15 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <20100401230843.GF3755@domain.hid> <4BB53566.3010601@domain.hid> <4BB53643.2080604@domain.hid> <4BB5AA44.6000006@domain.hid> <4BB5AACE.7020602@domain.hid> <4BB5B1BD.6020903@domain.hid> In-Reply-To: <4BB5B1BD.6020903@domain.hid> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig971E58ADB9AB54F88D3FE093" Sender: jan.kiszka@domain.hid Subject: Re: [Xenomai-help] New scheduler class List-Id: Help regarding installation and common use of Xenomai List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gilles Chanteperdrix Cc: xenomai@xenomai.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig971E58ADB9AB54F88D3FE093 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Jan Kiszka wrote: > Gilles Chanteperdrix wrote: >> Jan Kiszka wrote: >>> Gilles Chanteperdrix wrote: >>>> Jan Kiszka wrote: >>>>> Andreas Glatz wrote: >>>>>> Hi Philippe, >>>>>> >>>>>> At the Xenomai Users Meeting last year I asked you if Xenomai woul= d offer a possibility to lower the priority of certain Xenomai tasks belo= w that of Linux. We need this feature since we have tasks in our RT appli= cation which should only run when Linux is idle (A statistics collection = task which part of the RT application and hard to isolate from this appli= cation). >>>>>> >>>>> What prevents using a borderline thread (if you need to interact wi= th >>>>> blocking Xenomai services) with SCHED_OTHER and a Linux nice level = of 19? >>>> Well, this does not really guarantee that the thread will run only w= hen >>>> linux is idle. The thread will eat some cpu time, the nice level is = not >>>> a strict priority, as you know. >>> Where do you really need anything stricter? It's the opposite of "I n= eed >>> true 100% CPU for my task, and that forever." >>> >>>> But in fact, I wonder why Andreas wants >>>> a new scheduling policy for xenomai, what is needed, is simply a >>>> SCHED_IDLE (maybe it exists ?!) policy for Linux. >>>> >>> There is no such thing AFAIK. If you are concerned that some CPU >>> intensive low prio job eats too much CPU, you normally reduce its >>> nice-level and/or confine its CPU bandwidth via cgroups. >> SCHED_IDLE exists. >> >=20 > Ah, as "nice 20". Same mechanism, just another level. >=20 =2E..and before trying something else: "SCHED_IDLE: This is even weaker than nice 19, but its not a true idle timer scheduler in order to avoid to get into priority inversion problems which would deadlock the machine." Jan --------------enig971E58ADB9AB54F88D3FE093 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org iEYEARECAAYFAku1stMACgkQitSsb3rl5xSh0gCfRznCbMC84QxLLFAj5tt9cjp+ 2oMAniMBxZG3RpFqAIhMoKJ+L+AJTxg6 =knRo -----END PGP SIGNATURE----- --------------enig971E58ADB9AB54F88D3FE093--