From owner-freebsd-arch@FreeBSD.ORG Mon Apr 24 23:24:26 2006 Return-Path: X-Original-To: arch@freebsd.org Delivered-To: freebsd-arch@FreeBSD.ORG Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 958DC16A403 for ; Mon, 24 Apr 2006 23:24:26 +0000 (UTC) (envelope-from kabaev@gmail.com) Received: from wproxy.gmail.com (wproxy.gmail.com [64.233.184.226]) by mx1.FreeBSD.org (Postfix) with ESMTP id 0EC5643D46 for ; Mon, 24 Apr 2006 23:24:25 +0000 (GMT) (envelope-from kabaev@gmail.com) Received: by wproxy.gmail.com with SMTP id i12so1119360wra for ; Mon, 24 Apr 2006 16:24:25 -0700 (PDT) DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=beta; d=gmail.com; h=received:date:from:to:cc:subject:message-id:in-reply-to:references:x-mailer:mime-version:content-type; b=lGQlO+mrlxyLhx2eTxuVYJ4kvSYS/4PZHVsq3J+O2k9lnw+9tUGTrMYqtpayikODP7BIhJLNbxjkzw0WuEBqmE/pggLRs+uf3+TwcoR6b8mofr9yXsV0EWpQ0QFEd45W0uy2H3kQhUB36qU+Rr0s3UT5NeY5Gq5O80Z1Zlfc3ks= Received: by 10.54.62.6 with SMTP id k6mr1283942wra; Mon, 24 Apr 2006 16:24:25 -0700 (PDT) Received: from kan.dnsalias.net ( [24.63.93.195]) by mx.gmail.com with ESMTP id g7sm221446wra.2006.04.24.16.24.24; Mon, 24 Apr 2006 16:24:24 -0700 (PDT) Date: Mon, 24 Apr 2006 19:24:14 -0400 From: Alexander Kabaev To: Julian Elischer Message-ID: <20060424192414.0dbaa534@kan.dnsalias.net> In-Reply-To: <444C765B.7070803@elischer.org> References: <200604240633.k3O6XUJ0042841@chez.mckusick.com> <20060424064352.GA728@funkthat.com> <444C765B.7070803@elischer.org> X-Mailer: Sylpheed-Claws 2.0.0 (GTK+ 2.8.16; i386-portbld-freebsd7.0) Mime-Version: 1.0 Content-Type: multipart/signed; boundary=Sig_iTCP_znP1nl+B37C3il8aZO; protocol="application/pgp-signature"; micalg=PGP-SHA1 Cc: Kirk McKusick , arch@freebsd.org, John-Mark Gurney Subject: Re: Linus Torvalds on FreeBSD's Use of Copy-on-write X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 24 Apr 2006 23:24:26 -0000 --Sig_iTCP_znP1nl+B37C3il8aZO Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Sun, 23 Apr 2006 23:55:23 -0700 Julian Elischer wrote: > John-Mark Gurney wrote: >=20 > >Kirk McKusick wrote this message on Sun, Apr 23, 2006 at 23:33 -0700: > > =20 > > > >>Linus explained that while this may look good on specific > >>benchmarks, it actually introduces extra overhead, "the thing is, > >>the cost of > >> =20 > >> > > > >Has he benchmarked this to prove his point? And has he done it over > >realworld work loads, like Apache or another "standard" program > >instead of a microbenchmark designed especially to make COW look bad? > > =20 > > >=20 > Well no-one has even confirmed that freeBSD does all this > "page flipping" etc. I doubt that Linus has looked inside the BSD > kernels. He's probably just repeating what he's been told, and that's > so accurate, right? >=20 > I know that freeBSD developers have over the last few years also=20 > acknowledged that > the speed of modern CPUs vs. memeory speeds makes it often less > efficient to do certain optimisations than it used to be. >=20 >=20 >=20 >=20 > >As w/ all theories, w/o numbers, they are only theories till backed > >up w/ benchmarks. > > > >This isn't suppose to defend COW, but it is designed to ensure that > >people don't stop exploring just because someone says something... > > > > =20 > > > _______________________________________________ > freebsd-arch@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-arch > To unsubscribe, send any mail to > "freebsd-arch-unsubscribe@freebsd.org" The original zero-copy code was used to stream network data directly to an onboard SDRAM memory on an extension PCI card. Linus' notes about relative cost of memory-to-memory copies vs. TLB shootdowns and possible page access traps had little relevance there. -- Alexander Kabaev --=20 Alexander Kabaev --Sig_iTCP_znP1nl+B37C3il8aZO Content-Type: application/pgp-signature; name=signature.asc Content-Disposition: attachment; filename=signature.asc -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.2.2 (FreeBSD) iD8DBQFETV4nQ6z1jMm+XZYRAmb0AJ9wJUar/mwUJc7XwoCbcfTNR5j6WgCgn6xu HNu/4H0KgHUFtuWcyiXutpw= =MBNK -----END PGP SIGNATURE----- --Sig_iTCP_znP1nl+B37C3il8aZO--