From mboxrd@z Thu Jan 1 00:00:00 1970 From: Tim Blechmann Subject: Re: rt file i/o Date: Wed, 04 Nov 2009 18:32:41 +0100 Message-ID: <4AF1BAB9.5080104@klingt.org> References: <5bdc1c8b0911040743h7e4eaa08w97ac8287b806b54f@mail.gmail.com> <4AF1A327.3040103@klingt.org> <20091104171412.GB1702@opentech.at> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig6DD7F7EC97796937FE6B8AE8" Cc: y@opentech.at, Mark Knecht , linux-rt-users@vger.kernel.org To: Nicholas Mc Guire Return-path: Received: from mail.klingt.org ([86.59.21.178]:42660 "EHLO klingt.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754807AbZKDRco (ORCPT ); Wed, 4 Nov 2009 12:32:44 -0500 In-Reply-To: <20091104171412.GB1702@opentech.at> Sender: linux-rt-users-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig6DD7F7EC97796937FE6B8AE8 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable >> well, if i understand the rt howto correctly, _no_ disc access is >> allowed, neither from rt nor from non-rt threads, since it may produce= >> page faults, which introduce latencies ... >=20 > I would be supprised if the rt howto states that page-faults in non-rt > threads is a critical problem - that would not significantly impact RT > performance - atelast not the worst case - it will (as every other syst= em > load) impact the average case. so having a non-rt thread reading disk-f= iles > to a buffer and a rt-thread processing this buffer should be perfectly = 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 ... tim [1] http://rt.wiki.kernel.org/index.php/HOWTO:_Build_an_RT-application#Latenc= ies_caused_by_Page-faults --=20 tim@klingt.org http://tim.klingt.org Your mind will answer most questions if you learn to relax and wait for the answer. William S. Burroughs --------------enig6DD7F7EC97796937FE6B8AE8 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) iEYEARECAAYFAkrxur4ACgkQdL+4qsZfVstYpgCePUQEIXcvwptAXRSjzpX7G3+q jDMAn0m7ZU+G/o2gxUrCm8XkpfCP+GXz =cv2f -----END PGP SIGNATURE----- --------------enig6DD7F7EC97796937FE6B8AE8--