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=-2.5 required=3.0 tests=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 7B7E0C433E0 for ; Mon, 29 Jun 2020 19:06:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 622BE20663 for ; Mon, 29 Jun 2020 19:06:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730726AbgF2TGF (ORCPT ); Mon, 29 Jun 2020 15:06:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41726 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730406AbgF2TCn (ORCPT ); Mon, 29 Jun 2020 15:02:43 -0400 X-Greylist: delayed 1419 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Mon, 29 Jun 2020 07:16:46 PDT Received: from www62.your-server.de (www62.your-server.de [IPv6:2a01:4f8:d0a:276a::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 337D4C02E2E8; Mon, 29 Jun 2020 07:16:46 -0700 (PDT) Received: from sslproxy03.your-server.de ([88.198.220.132]) by www62.your-server.de with esmtpsa (TLSv1.2:DHE-RSA-AES256-GCM-SHA384:256) (Exim 4.89_1) (envelope-from ) id 1jpuDM-0001DH-6o; Mon, 29 Jun 2020 15:52:52 +0200 Received: from [178.196.57.75] (helo=pc-9.home) by sslproxy03.your-server.de with esmtpsa (TLSv1.3:TLS_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1jpuDL-0002Xa-QH; Mon, 29 Jun 2020 15:52:51 +0200 Subject: Re: [PATCH net] xsk: remove cheap_dma optimization To: =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , Christoph Hellwig Cc: =?UTF-8?B?QmrDtnJuIFTDtnBlbA==?= , netdev@vger.kernel.org, davem@davemloft.net, konrad.wilk@oracle.com, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, maximmi@mellanox.com, magnus.karlsson@intel.com, jonathan.lemon@gmail.com References: <20200626134358.90122-1-bjorn.topel@gmail.com> <20200627070406.GB11854@lst.de> <88d27e1b-dbda-301c-64ba-2391092e3236@intel.com> From: Daniel Borkmann Message-ID: Date: Mon, 29 Jun 2020 15:52:51 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.2 MIME-Version: 1.0 In-Reply-To: <88d27e1b-dbda-301c-64ba-2391092e3236@intel.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit X-Authenticated-Sender: daniel@iogearbox.net X-Virus-Scanned: Clear (ClamAV 0.102.3/25857/Sun Jun 28 15:28:36 2020) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/28/20 7:16 PM, Björn Töpel wrote: > On 2020-06-27 09:04, Christoph Hellwig wrote: >> On Sat, Jun 27, 2020 at 01:00:19AM +0200, Daniel Borkmann wrote: >>> Given there is roughly a ~5 weeks window at max where this removal could >>> still be applied in the worst case, could we come up with a fix / proposal >>> first that moves this into the DMA mapping core? If there is something that >>> can be agreed upon by all parties, then we could avoid re-adding the 9% >>> slowdown. :/ >> >> I'd rather turn it upside down - this abuse of the internals blocks work >> that has basically just missed the previous window and I'm not going >> to wait weeks to sort out the API misuse.  But we can add optimizations >> back later if we find a sane way. > > I'm not super excited about the performance loss, but I do get > Christoph's frustration about gutting the DMA API making it harder for > DMA people to get work done. Lets try to solve this properly using > proper DMA APIs. Ok, fair enough, please work with DMA folks to get this properly integrated and restored then. Applied, thanks!