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 1DB24C4646D for ; Mon, 6 Aug 2018 09:02:45 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C5647219EB for ; Mon, 6 Aug 2018 09:02:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C5647219EB Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.vnet.ibm.com 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 S1727174AbeHFLKr (ORCPT ); Mon, 6 Aug 2018 07:10:47 -0400 Received: from mx0a-001b2d01.pphosted.com ([148.163.156.1]:56344 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726468AbeHFLKq (ORCPT ); Mon, 6 Aug 2018 07:10:46 -0400 Received: from pps.filterd (m0098394.ppops.net [127.0.0.1]) by mx0a-001b2d01.pphosted.com (8.16.0.22/8.16.0.22) with SMTP id w768xTti099252 for ; Mon, 6 Aug 2018 05:02:41 -0400 Received: from e06smtp07.uk.ibm.com (e06smtp07.uk.ibm.com [195.75.94.103]) by mx0a-001b2d01.pphosted.com with ESMTP id 2kphw7udky-1 (version=TLSv1.2 cipher=AES256-GCM-SHA384 bits=256 verify=NOT) for ; Mon, 06 Aug 2018 05:02:41 -0400 Received: from localhost by e06smtp07.uk.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Mon, 6 Aug 2018 10:02:38 +0100 Received: from b06cxnps4076.portsmouth.uk.ibm.com (9.149.109.198) by e06smtp07.uk.ibm.com (192.168.101.137) with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted; (version=TLSv1/SSLv3 cipher=AES256-GCM-SHA384 bits=256/256) Mon, 6 Aug 2018 10:02:34 +0100 Received: from d06av26.portsmouth.uk.ibm.com (d06av26.portsmouth.uk.ibm.com [9.149.105.62]) by b06cxnps4076.portsmouth.uk.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id w7692X2J41812140 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 6 Aug 2018 09:02:33 GMT Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id D8AC9AE057; Mon, 6 Aug 2018 12:02:28 +0100 (BST) Received: from d06av26.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id 38D24AE061; Mon, 6 Aug 2018 12:02:25 +0100 (BST) Received: from [9.202.14.95] (unknown [9.202.14.95]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Mon, 6 Aug 2018 12:02:24 +0100 (BST) Subject: Re: [RFC 0/4] Virtio uses DMA API for all devices To: "Michael S. Tsirkin" , Benjamin Herrenschmidt References: <20180720035941.6844-1-khandual@linux.vnet.ibm.com> <20180802235332-mutt-send-email-mst@kernel.org> <20180803220812-mutt-send-email-mst@kernel.org> <01c74680c4b3aa25d9b4375a9ab5e10046b7c71b.camel@kernel.crashing.org> <20180805032355-mutt-send-email-mst@kernel.org> Cc: robh@kernel.org, srikar@linux.vnet.ibm.com, aik@ozlabs.ru, Jason Wang , linuxram@us.ibm.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, hch@infradead.org, paulus@samba.org, joe@perches.com, david@gibson.dropbear.id.au, linuxppc-dev@lists.ozlabs.org, elfring@users.sourceforge.net, haren@linux.vnet.ibm.com From: Anshuman Khandual Date: Mon, 6 Aug 2018 14:32:28 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.5.1 MIME-Version: 1.0 In-Reply-To: <20180805032355-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 x-cbid: 18080609-0028-0000-0000-000002E61743 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 18080609-0029-0000-0000-0000239E3834 Message-Id: <74a1e1b8-81e0-84db-6d0d-d8bd9caebb4a@linux.vnet.ibm.com> X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-08-06_05:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1807170000 definitions=main-1808060099 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 08/05/2018 05:54 AM, Michael S. Tsirkin wrote: > On Fri, Aug 03, 2018 at 08:21:26PM -0500, Benjamin Herrenschmidt wrote: >> 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. > > I won't be surprised. If yes I suggested a way to mitigate the overhead. Did we get better results (lower regression due to indirect calls) with the suggested mitigation ? Just curious. From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anshuman Khandual Subject: Re: [RFC 0/4] Virtio uses DMA API for all devices Date: Mon, 6 Aug 2018 14:32:28 +0530 Message-ID: <74a1e1b8-81e0-84db-6d0d-d8bd9caebb4a@linux.vnet.ibm.com> References: <20180720035941.6844-1-khandual@linux.vnet.ibm.com> <20180802235332-mutt-send-email-mst@kernel.org> <20180803220812-mutt-send-email-mst@kernel.org> <01c74680c4b3aa25d9b4375a9ab5e10046b7c71b.camel@kernel.crashing.org> <20180805032355-mutt-send-email-mst@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20180805032355-mutt-send-email-mst@kernel.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: "Michael S. Tsirkin" , Benjamin Herrenschmidt Cc: robh@kernel.org, srikar@linux.vnet.ibm.com, linuxram@us.ibm.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, hch@infradead.org, paulus@samba.org, joe@perches.com, linuxppc-dev@lists.ozlabs.org, elfring@users.sourceforge.net, haren@linux.vnet.ibm.com, david@gibson.dropbear.id.au List-Id: virtualization@lists.linuxfoundation.org On 08/05/2018 05:54 AM, Michael S. Tsirkin wrote: > On Fri, Aug 03, 2018 at 08:21:26PM -0500, Benjamin Herrenschmidt wrote: >> 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. > > I won't be surprised. If yes I suggested a way to mitigate the overhead. Did we get better results (lower regression due to indirect calls) with the suggested mitigation ? Just curious.