From mboxrd@z Thu Jan 1 00:00:00 1970 Received: with ECARTIS (v1.0.0; list linux-mips); Fri, 04 Oct 2002 16:14:34 +0200 (CEST) Received: from mx2.mips.com ([206.31.31.227]:21120 "EHLO mx2.mips.com") by linux-mips.org with ESMTP id ; Fri, 4 Oct 2002 16:14:33 +0200 Received: from newman.mips.com (ns-dmz [206.31.31.225]) by mx2.mips.com (8.12.5/8.12.5) with ESMTP id g94EEONf016525; Fri, 4 Oct 2002 07:14:24 -0700 (PDT) Received: from grendel (grendel [192.168.236.16]) by newman.mips.com (8.9.3/8.9.0) with SMTP id HAA02433; Fri, 4 Oct 2002 07:14:51 -0700 (PDT) Message-ID: <016201c26bb0$b8609a30$10eca8c0@grendel> From: "Kevin D. Kissell" To: "Alan Cox" Cc: References: <3D9D484B.4C149BD8@mips.com><200210041153.MAA12052@mudchute.algor.co.uk><3D9D855B.12128FA2@mips.com><1033734968.31839.5.camel@irongate.swansea.linux .org.uk> <00fe01c26ba6$04943480$10eca8c0@grendel><1033737330.31861.30.camel@irongate.swansea.linux.org.uk> <010e01c26ba8$2c9400d0$10eca8c0@grendel> <1033739046.31861.35.camel@irongate.swansea.linux.org.uk> Subject: Re: Promblem with PREF (prefetching) in memcpy Date: Fri, 4 Oct 2002 16:17:01 +0200 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.50.4807.1700 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4910.0300 Return-Path: X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0) X-Orcpt: rfc822;linux-mips@linux-mips.org Original-Recipient: rfc822;linux-mips@linux-mips.org X-archive-position: 374 X-ecartis-version: Ecartis v1.0.0 Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org X-original-sender: kevink@mips.com Precedence: bulk X-list: linux-mips From: "Alan Cox" > On Fri, 2002-10-04 at 14:15, Kevin D. Kissell wrote: > > Which is excatly the point that Carsten was raising when he started this thread! > > > > The question is how, i.e. throttle memcpy or thow away a "guard band" of RAM? > > > The x86 code basically says > > while(over 320 bytes left) > { > prefetch ahead > copy bits > } > while(bytes left) > copy bits Which is safe, simple, and efficient, but does seem to have the property that there's a "cursed" page in the system that can be randomly allocated and which will be curiously slow on memcopy(). That might or might not be a problem in the embedded application space. Regards, Kevin K. From mboxrd@z Thu Jan 1 00:00:00 1970 Message-ID: <016201c26bb0$b8609a30$10eca8c0@grendel> From: "Kevin D. Kissell" References: <3D9D484B.4C149BD8@mips.com><200210041153.MAA12052@mudchute.algor.co.uk><3D9D855B.12128FA2@mips.com><1033734968.31839.5.camel@irongate.swansea.linux .org.uk> <00fe01c26ba6$04943480$10eca8c0@grendel><1033737330.31861.30.camel@irongate.swansea.linux.org.uk> <010e01c26ba8$2c9400d0$10eca8c0@grendel> <1033739046.31861.35.camel@irongate.swansea.linux.org.uk> Subject: Re: Promblem with PREF (prefetching) in memcpy Date: Fri, 4 Oct 2002 16:17:01 +0200 MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Return-Path: Sender: linux-mips-bounce@linux-mips.org Errors-to: linux-mips-bounce@linux-mips.org To: Alan Cox Cc: linux-mips@linux-mips.org Message-ID: <20021004141701.IwkMaMn9OX6Qq_Obghrp7X0j5pqGyncr_P1s21SEW1s@z> From: "Alan Cox" > On Fri, 2002-10-04 at 14:15, Kevin D. Kissell wrote: > > Which is excatly the point that Carsten was raising when he started this thread! > > > > The question is how, i.e. throttle memcpy or thow away a "guard band" of RAM? > > > The x86 code basically says > > while(over 320 bytes left) > { > prefetch ahead > copy bits > } > while(bytes left) > copy bits Which is safe, simple, and efficient, but does seem to have the property that there's a "cursed" page in the system that can be randomly allocated and which will be curiously slow on memcopy(). That might or might not be a problem in the embedded application space. Regards, Kevin K.