From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CA21DC433E2 for ; Sun, 6 Sep 2020 18:21:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 8F6A22078E for ; Sun, 6 Sep 2020 18:21:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729140AbgIFSV1 (ORCPT ); Sun, 6 Sep 2020 14:21:27 -0400 Received: from jabberwock.ucw.cz ([46.255.230.98]:43378 "EHLO jabberwock.ucw.cz" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728969AbgIFSV0 (ORCPT ); Sun, 6 Sep 2020 14:21:26 -0400 Received: by jabberwock.ucw.cz (Postfix, from userid 1017) id 7B16E1C0B7C; Sun, 6 Sep 2020 20:21:23 +0200 (CEST) Date: Sun, 6 Sep 2020 20:21:22 +0200 From: Pavel Machek To: David Laight Cc: 'Christophe Leroy' , Christoph Hellwig , "arnd@arndb.de" , "gregkh@linuxfoundation.org" , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH] /dev/zero: also implement ->read Message-ID: <20200906182122.GA12295@amd> References: <20200903155922.1111551-1-hch@lst.de> <55d1ecb8-4a0c-fa58-d3cf-bf6796eea7bd@csgroup.eu> <3b0b58be4b844162b73db1b108a9b995@AcuMS.aculab.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="G4iJoqBmSsgzjUCe" Content-Disposition: inline In-Reply-To: <3b0b58be4b844162b73db1b108a9b995@AcuMS.aculab.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --G4iJoqBmSsgzjUCe Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hi! > > > Christophe reported a major speedup due to avoiding the iov_iter > > > overhead, so just add this trivial function. Note that /dev/zero > > > already implements both an iter and non-iter writes so this just > > > makes it more symmetric. > > > > > > Christophe Leroy > > > Signed-off-by: Christoph Hellwig > >=20 > > Tested-by: Christophe Leroy >=20 > Any idea what has happened to make the 'iter' version so bad? Exactly. Also it would be nice to note how the speedup was measured and what the speedup is. Best regads, Pavel --=20 (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blo= g.html --G4iJoqBmSsgzjUCe Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iEYEARECAAYFAl9VKKIACgkQMOfwapXb+vKZlwCdFfFAEv0cdTUQKC8HL8e4o4qF jgYAmwbYMoMEhknMT1mDu4MFPQbcO3/d =vvM5 -----END PGP SIGNATURE----- --G4iJoqBmSsgzjUCe--