From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: application needs fast access to physical memory From: Michael Ellerman To: steven.lin@teradyne.com In-Reply-To: References: Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-RDW1osiPoH6TkmM8GwYX" Date: Thu, 18 Nov 2010 23:24:22 +1100 Message-ID: <1290083062.22575.9.camel@concordia> Mime-Version: 1.0 Cc: Steven_Lin@notes.teradyne.com, linuxppc-dev@lists.ozlabs.org Reply-To: michael@ellerman.id.au List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , --=-RDW1osiPoH6TkmM8GwYX Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, 2010-11-17 at 16:03 -0600, steven.lin@teradyne.com wrote: > My application needs a fast way to access a specific physical DDR > memory region. The application runs on an MPC8548 PowerPC which has an > MMU. I've tried two approaches that are typical for Linux, mmap() and > using a kernel module that implements read()/write() into this region > and I'm finding that performance is very slow for both. It's a couple > orders of magnitude slower than, for example, copying a large buffer > from one place in the application's virtual memory to another place in > the application's virtual memory. The mmap() version should basically run at "full speed", at least once you've faulted the address range in. This specific DDR region isn't specifically slow is it ? :) cheers --=-RDW1osiPoH6TkmM8GwYX Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) iEYEABECAAYFAkzlGvYACgkQdSjSd0sB4dJzkgCfZEiWFy/9AMpXECJTw9r/7JSR 3bAAoMecPYt9rv2p3zIVJY/S9/7jq6EZ =bcNT -----END PGP SIGNATURE----- --=-RDW1osiPoH6TkmM8GwYX--