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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no 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 C2542C43466 for ; Mon, 21 Sep 2020 16:12:30 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 4999E20708 for ; Mon, 21 Sep 2020 16:12:30 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 4999E20708 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id BFF0290008C; Mon, 21 Sep 2020 12:12:29 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B8840900083; Mon, 21 Sep 2020 12:12:29 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A286390008C; Mon, 21 Sep 2020 12:12:29 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0165.hostedemail.com [216.40.44.165]) by kanga.kvack.org (Postfix) with ESMTP id 8177A900083 for ; Mon, 21 Sep 2020 12:12:29 -0400 (EDT) Received: from smtpin25.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id 2744C180AD806 for ; Mon, 21 Sep 2020 16:12:29 +0000 (UTC) X-FDA: 77287561218.25.shelf23_3901ab027146 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin25.hostedemail.com (Postfix) with ESMTP id EA5FB1804E3A0; Mon, 21 Sep 2020 16:12:28 +0000 (UTC) X-HE-Tag: shelf23_3901ab027146 X-Filterd-Recvd-Size: 2545 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by imf32.hostedemail.com (Postfix) with ESMTP; Mon, 21 Sep 2020 16:12:27 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id AF5CF68B02; Mon, 21 Sep 2020 18:12:24 +0200 (CEST) Date: Mon, 21 Sep 2020 18:12:24 +0200 From: Christoph Hellwig To: Al Viro Cc: David Laight , Christoph Hellwig , Andrew Morton , Jens Axboe , Arnd Bergmann , David Howells , "linux-arm-kernel@lists.infradead.org" , "linux-kernel@vger.kernel.org" , "linux-mips@vger.kernel.org" , "linux-parisc@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-s390@vger.kernel.org" , "sparclinux@vger.kernel.org" , "linux-block@vger.kernel.org" , "linux-scsi@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-aio@kvack.org" , "io-uring@vger.kernel.org" , "linux-arch@vger.kernel.org" , "linux-mm@kvack.org" , "netdev@vger.kernel.org" , "keyrings@vger.kernel.org" , "linux-security-module@vger.kernel.org" Subject: Re: [PATCH 02/11] mm: call import_iovec() instead of rw_copy_check_uvector() in process_vm_rw() Message-ID: <20200921161224.GA24807@lst.de> References: <20200921143434.707844-1-hch@lst.de> <20200921143434.707844-3-hch@lst.de> <20200921150211.GS3421308@ZenIV.linux.org.uk> <20200921152937.GX3421308@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200921152937.GX3421308@ZenIV.linux.org.uk> User-Agent: Mutt/1.5.17 (2007-11-01) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Sep 21, 2020 at 04:29:37PM +0100, Al Viro wrote: > On Mon, Sep 21, 2020 at 03:21:35PM +0000, David Laight wrote: > > > You really don't want to be looping through the array twice. > > Profiles, please. Given that the iov array should be cache hot I'd be surprised to see a huge difference.