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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 57FB0C28CF6 for ; Sat, 4 Aug 2018 02:41:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 094672175E for ; Sat, 4 Aug 2018 02:41:33 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 094672175E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.crashing.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726753AbeHDEjs (ORCPT ); Sat, 4 Aug 2018 00:39:48 -0400 Received: from gate.crashing.org ([63.228.1.57]:33782 "EHLO gate.crashing.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725792AbeHDEjs (ORCPT ); Sat, 4 Aug 2018 00:39:48 -0400 Received: from localhost (localhost.localdomain [127.0.0.1]) by gate.crashing.org (8.14.1/8.14.1) with ESMTP id w741LQMO023472; Fri, 3 Aug 2018 20:21:27 -0500 Message-ID: <01c74680c4b3aa25d9b4375a9ab5e10046b7c71b.camel@kernel.crashing.org> Subject: Re: [RFC 0/4] Virtio uses DMA API for all devices From: Benjamin Herrenschmidt To: "Michael S. Tsirkin" , Jason Wang Cc: Anshuman Khandual , virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, aik@ozlabs.ru, robh@kernel.org, joe@perches.com, elfring@users.sourceforge.net, david@gibson.dropbear.id.au, mpe@ellerman.id.au, hch@infradead.org, linuxram@us.ibm.com, haren@linux.vnet.ibm.com, paulus@samba.org, srikar@linux.vnet.ibm.com Date: Fri, 03 Aug 2018 20:21:26 -0500 In-Reply-To: <20180803220812-mutt-send-email-mst@kernel.org> References: <20180720035941.6844-1-khandual@linux.vnet.ibm.com> <20180802235332-mutt-send-email-mst@kernel.org> <20180803220812-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.28.4 (3.28.4-1.fc28) Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2018-08-03 at 22:08 +0300, Michael S. Tsirkin wrote: > > > > Please go through these patches and review whether this approach broadly > > > > makes sense. I will appreciate suggestions, inputs, comments regarding > > > > the patches or the approach in general. Thank you. > > > > > > Jason did some work on profiling this. Unfortunately he reports > > > about 4% extra overhead from this switch on x86 with no vIOMMU. > > > > The test is rather simple, just run pktgen (pktgen_sample01_simple.sh) in > > guest and measure PPS on tap on host. > > > > Thanks > > Could you supply host configuration involved please? I wonder how much of that could be caused by Spectre mitigations blowing up indirect function calls... Cheers, Ben.