Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261176AbTIJJXZ (ORCPT ); Wed, 10 Sep 2003 05:23:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261185AbTIJJXY (ORCPT ); Wed, 10 Sep 2003 05:23:24 -0400 Received: from node-d-1ea6.a2000.nl ([62.195.30.166]:17135 "EHLO laptop.fenrus.com") by vger.kernel.org with ESMTP id S261176AbTIJJXX (ORCPT ); Wed, 10 Sep 2003 05:23:23 -0400 Subject: Re: Efficient IPC mechanism on Linux From: Arjan van de Ven Reply-To: arjanv@redhat.com To: Luca Veraldi Cc: alexander.riesen@synopsys.COM, linux-kernel In-Reply-To: <015601c3777c$8c63b2e0$5aaf7450@wssupremo> References: <00f201c376f8$231d5e00$beae7450@wssupremo> <20030909175821.GL16080@Synopsys.COM> <001d01c37703$8edc10e0$36af7450@wssupremo> <20030910064508.GA25795@Synopsys.COM> <015601c3777c$8c63b2e0$5aaf7450@wssupremo> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="=-piKTnjf3Fco8CbRH+MsD" Organization: Red Hat, Inc. Message-Id: <1063185795.5021.4.camel@laptop.fenrus.com> Mime-Version: 1.0 X-Mailer: Ximian Evolution 1.4.4 (1.4.4-4) Date: Wed, 10 Sep 2003 11:23:15 +0200 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1311 Lines: 37 --=-piKTnjf3Fco8CbRH+MsD Content-Type: text/plain Content-Transfer-Encoding: quoted-printable On Wed, 2003-09-10 at 11:18, Luca Veraldi wrote: > The overhead implied by a memcpy() is the same, in the oder of magnitude, > ***whatever*** kernel version you can develop. yes a copy of a page is about 3000 to 4000 cycles on an x86 box in the uncached case. A pagetable operation (like the cpu setting the accessed or dirty bit) is in that same order I suspect (maybe half this, but not a lot less). Changing pagetable content is even more because all the tlb's and internal cpu state will need to be flushed... which is also a microcode operation for the cpu. And it's deadly in an SMP environment. --=-piKTnjf3Fco8CbRH+MsD Content-Type: application/pgp-signature; name=signature.asc Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.2 (GNU/Linux) iD8DBQA/Xu2DxULwo51rQBIRAihBAJ9bDCKvKT7UD4YhEobUbAzPtiKMxQCeJc3y VzJH9CbmiDxXBWYavImXX8Y= =pVNA -----END PGP SIGNATURE----- --=-piKTnjf3Fco8CbRH+MsD-- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/