From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tim Blechmann Subject: Re: rt file i/o Date: Thu, 05 Nov 2009 10:29:58 +0100 Message-ID: <4AF29B16.1000104@klingt.org> References: <5bdc1c8b0911040743h7e4eaa08w97ac8287b806b54f@mail.gmail.com> <4AF1A327.3040103@klingt.org> <20091104171412.GB1702@opentech.at> <4AF1BAB9.5080104@klingt.org> <20091104164413.3aff479c@torg> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigAB1177ED4C13DF7F062D1A62" Cc: Nicholas Mc Guire , y@opentech.at, Mark Knecht , linux-rt-users@vger.kernel.org To: Clark Williams Return-path: Received: from mail.klingt.org ([86.59.21.178]:36703 "EHLO klingt.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752029AbZKEJaP (ORCPT ); Thu, 5 Nov 2009 04:30:15 -0500 In-Reply-To: <20091104164413.3aff479c@torg> Sender: linux-rt-users-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigAB1177ED4C13DF7F062D1A62 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 11/04/2009 11:44 PM, Clark Williams wrote: > On Wed, 04 Nov 2009 18:32:41 +0100 > Tim Blechmann wrote: >=20 >>>> well, if i understand the rt howto correctly, _no_ disc access is >>>> allowed, neither from rt nor from non-rt threads, since it may produ= ce >>>> page faults, which introduce latencies ... >>> >>> I would be supprised if the rt howto states that page-faults in non-r= t >>> threads is a critical problem - that would not significantly impact R= T >>> performance - atelast not the worst case - it will (as every other sy= stem >>> load) impact the average case. so having a non-rt thread reading disk= -files >>> to a buffer and a rt-thread processing this buffer should be perfectl= y fine. >> >> that is what i thought for years ... but according to [1] a page fault= >> in an rt process freezes the entire process with both rt and non-rt >> threads until the page fault is handled ... >> >=20 > No, we need to get that fixed in the wiki. It may have been the case > that the entire process was frozen while a fault was being handled, but= > I don't believe that is the case now. If you're in a thread on core0 > and a sibling thread on core1 faults, you shouldn't be impacted unless > you're trying to reference the same memory.=20 well, then my application seems to be real-time safe ... it would be nice if the wiki would reflect the current state of the rt-preempt kernel, though ... thnx, tim --=20 tim@klingt.org http://tim.klingt.org All we composers really have to work with is time and sound - and sometimes I'm not even sure about sound. Morton Feldman --------------enigAB1177ED4C13DF7F062D1A62 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (GNU/Linux) iEYEARECAAYFAkrymxkACgkQdL+4qsZfVssMnQCbB84oz7Z72hr0pKJ5bDO3M7oj eA0AnjKv29G5vzz+2vaOQYA/X5lYETJZ =BoFe -----END PGP SIGNATURE----- --------------enigAB1177ED4C13DF7F062D1A62--