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,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 255CEC433E1 for ; Sat, 27 Jun 2020 07:04:13 +0000 (UTC) Received: from whitealder.osuosl.org (smtp1.osuosl.org [140.211.166.138]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 0524420857 for ; Sat, 27 Jun 2020 07:04:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0524420857 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=lst.de Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by whitealder.osuosl.org (Postfix) with ESMTP id BCE93879FD; Sat, 27 Jun 2020 07:04:12 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from whitealder.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Smj1ymNoFKHy; Sat, 27 Jun 2020 07:04:12 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by whitealder.osuosl.org (Postfix) with ESMTP id 380F381435; Sat, 27 Jun 2020 07:04:12 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 1BF15C0863; Sat, 27 Jun 2020 07:04:12 +0000 (UTC) Received: from fraxinus.osuosl.org (smtp4.osuosl.org [140.211.166.137]) by lists.linuxfoundation.org (Postfix) with ESMTP id 7E834C016F for ; Sat, 27 Jun 2020 07:04:10 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by fraxinus.osuosl.org (Postfix) with ESMTP id 7ACAB868CB for ; Sat, 27 Jun 2020 07:04:10 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from fraxinus.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id MTTLGRVxr_8E for ; Sat, 27 Jun 2020 07:04:10 +0000 (UTC) X-Greylist: from auto-whitelisted by SQLgrey-1.7.6 Received: from verein.lst.de (verein.lst.de [213.95.11.211]) by fraxinus.osuosl.org (Postfix) with ESMTPS id E624685582 for ; Sat, 27 Jun 2020 07:04:09 +0000 (UTC) Received: by verein.lst.de (Postfix, from userid 2407) id 229C568B02; Sat, 27 Jun 2020 09:04:07 +0200 (CEST) Date: Sat, 27 Jun 2020 09:04:06 +0200 From: Christoph Hellwig To: Daniel Borkmann Subject: Re: [PATCH net] xsk: remove cheap_dma optimization Message-ID: <20200627070406.GB11854@lst.de> References: <20200626134358.90122-1-bjorn.topel@gmail.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) Cc: maximmi@mellanox.com, konrad.wilk@oracle.com, jonathan.lemon@gmail.com, linux-kernel@vger.kernel.org, hch@lst.de, iommu@lists.linux-foundation.org, netdev@vger.kernel.org, bpf@vger.kernel.org, =?iso-8859-1?Q?Bj=F6rn_T=F6pel?= , davem@davemloft.net, magnus.karlsson@intel.com X-BeenThere: iommu@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Development issues for Linux IOMMU support List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" 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. That being said I really can't see how this would make so much of a difference. What architecture and what dma_ops are you using for those measurements? What is the workload? _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu