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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,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 DA3F2C43461 for ; Tue, 8 Sep 2020 19:42:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9D67C20578 for ; Tue, 8 Sep 2020 19:42:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732179AbgIHTmh (ORCPT ); Tue, 8 Sep 2020 15:42:37 -0400 Received: from verein.lst.de ([213.95.11.211]:53187 "EHLO verein.lst.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730890AbgIHPwt (ORCPT ); Tue, 8 Sep 2020 11:52:49 -0400 Received: by verein.lst.de (Postfix, from userid 2407) id B629F68B05; Tue, 8 Sep 2020 17:52:28 +0200 (CEST) Date: Tue, 8 Sep 2020 17:52:28 +0200 From: Christoph Hellwig To: Maor Gottlieb Cc: Christoph Hellwig , Leon Romanovsky , Doug Ledford , Jason Gunthorpe , linux-kernel@vger.kernel.org, linux-rdma@vger.kernel.org Subject: Re: [PATCH rdma-next 1/4] lib/scatterlist: Refactor sg_alloc_table_from_pages Message-ID: <20200908155228.GA13593@lst.de> References: <20200903121853.1145976-1-leon@kernel.org> <20200903155434.1153934-1-leon@kernel.org> <20200907072912.GA19875@lst.de> <2a4b0211-c7a0-2a82-1335-7ed935b92aa2@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <2a4b0211-c7a0-2a82-1335-7ed935b92aa2@nvidia.com> User-Agent: Mutt/1.5.17 (2007-11-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Sep 07, 2020 at 03:32:31PM +0300, Maor Gottlieb wrote: > > On 9/7/2020 10:29 AM, Christoph Hellwig wrote: >> On Thu, Sep 03, 2020 at 06:54:34PM +0300, Leon Romanovsky wrote: >>> From: Maor Gottlieb >>> >>> Currently, sg_alloc_table_from_pages doesn't support dynamic chaining of >>> SG entries. Therefore it requires from user to allocate all the pages in >>> advance and hold them in a large buffer. Such a buffer consumes a lot of >>> temporary memory in HPC systems which do a very large memory registration. >>> >>> The next patches introduce API for dynamically allocation from pages and >>> it requires us to do the following: >>> * Extract the code to alloc_from_pages_common. >>> * Change the build of the table to iterate on the chunks and not on the >>> SGEs. It will allow dynamic allocation of more SGEs. >>> >>> Since sg_alloc_table_from_pages allocate exactly the number of chunks, >>> therefore chunks are equal to the number of SG entries. >> Given how few users __sg_alloc_table_from_pages has, what about just >> switching it to your desired calling conventions without another helper? > > I tried it now. It didn't save a lot.  Please give me your decision and if > needed I will update accordingly. Feel free to keep it for now, we can sort this out later.