From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <44903372.2010104@domain.hid> Date: Wed, 14 Jun 2006 18:04:02 +0200 From: Jan Kiszka MIME-Version: 1.0 Subject: Re: [Xenomai-core] ns vs. tsc as internal timer base References: <448E98A3.6080707@domain.hid> <448E9E8B.70809@domain.hid> <448EA7F7.5000802@domain.hid> <448EB038.8070802@domain.hid> <448EE593.7010809@domain.hid> <448EF022.1040901@domain.hid> <17550.61982.685449.470866@domain.hid> <448EFCC5.60308@domain.hid> <448FD5EC.4060109@domain.hid> <44900143.50806@domain.hid> <44900A19.1040702@domain.hid> In-Reply-To: <44900A19.1040702@domain.hid> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig720BD8951FB504CD82A429CB" Sender: jan.kiszka@domain.hid List-Id: "Xenomai life and development \(bug reports, patches, discussions\)" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Philippe Gerum Cc: xenomai-core This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig720BD8951FB504CD82A429CB Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: quoted-printable Jan Kiszka wrote: > Philippe Gerum wrote: >> Jim Cromie wrote: >>> Philippe Gerum wrote: >>> >>>> Gilles Chanteperdrix wrote: >>>> >>>>> Philippe Gerum wrote: >>>>> > Redone the check here on a Centrino 1.6Mhz, and still have >>>>> roughly x20 > improvement (a bit better actually). I'm using >>>>> Debian/sarge gcc 3.3.5. >>>>> >>>>> I think I remember that Pentium M has a much shorter mull instructi= on >>>>> than other processors of the family. >>>>> >>>> That would explain. Anyway, as John Stulz put it: >>>> "math is hard, lets go shopping!" >>>> >>> Heh. Appropriate that his name (Stultz) comes up here, as his >>> generic-time (GTOD) >>> patchset looks headed for 2.6.18, bringing with it a full re-working >>> of linux timers / timeofday. IN this new world, time is kept on >>> free-running counters. >>> >>> Ive been running this patchset on my soekris for some time, since >>> GTOD detects that the TSC counts slowly, calls it insane, and does ti= ming >>> with the PIT. >>> >>> With GTOD, writing a new clocksource driver is easy, enough so I coul= d >>> do it. >>> My clocksource patch uses the 27 mhz timer on the Geode CPU. >>> Once the TSC is de-rated, mine becomes the best clocksource, and GTOD= >>> switches to it. >>> >>> All of which is to say .. >>> new mainline code is coming, should this current rework notion wait, >>> given that its will all need revisited again later >>> >> Clearly yes, since this is going to impact Adeos too. GTOD is going to= >> fiddle with the PIT channels in a way Adeos needs to be aware of, in >> order for the client RTOS to reuse such timer. Added to the flow of >> other core changes planned for 2.6.18, this is likely going to be funk= y. >> >> "Find wall. Beat head against same." >> >=20 > May not be required: the GTOD and clocksource abstractions could provid= e > a clean way to register some virtual, Adeos- or RTOS-provided clock wit= h > Linux. And that clock may even lose ticks without Linux losing its > system time! So far for the theory, practice may still require walls...= >=20 Some refinement: clocksource may either remain TSC or become a Xenomai-provided clock if its handling (PIT...) requires synchronisation. The clockevent, the one thing that triggers timer IRQs, could become a virtual device driven by Xenomai. And GTOD should happily make use of them instead of messing up with shared hardware. Jan --------------enig720BD8951FB504CD82A429CB 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 iD8DBQFEkDNzniDOoMHTA+kRAqTVAJ9b1+T5sPKKJeNhcnGr2eGAi5czggCfWIp4 twLrmtwEqY+lES+s1UnityA= =gFX3 -----END PGP SIGNATURE----- --------------enig720BD8951FB504CD82A429CB--