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=-5.9 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 A2DE2C47092 for ; Thu, 3 Jun 2021 00:40:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 86F23613E6 for ; Thu, 3 Jun 2021 00:40:48 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229626AbhFCAmb (ORCPT ); Wed, 2 Jun 2021 20:42:31 -0400 Received: from mga14.intel.com ([192.55.52.115]:39200 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229765AbhFCAm1 (ORCPT ); Wed, 2 Jun 2021 20:42:27 -0400 IronPort-SDR: GGionNQvg+GYWF0JfYblB7iRUNvsKrTyK6OlrQ3sT+wOH6g01moQBrK8j4ZBNZjCKrGM6b/yp5 r9mAhl1G9b8w== X-IronPort-AV: E=McAfee;i="6200,9189,10003"; a="203744510" X-IronPort-AV: E=Sophos;i="5.83,244,1616482800"; d="scan'208";a="203744510" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga103.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Jun 2021 17:40:41 -0700 IronPort-SDR: Zuk+nNOCyvGKNhXUc2GuhSRJJq7uWU0Z2qGQgUjj3tsrsLZtCpucKreWSZa8oFeMkPS9WLWbpW pdMsgDgnlHzw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.83,244,1616482800"; d="scan'208";a="633512059" Received: from allen-box.sh.intel.com (HELO [10.239.159.105]) ([10.239.159.105]) by fmsmga006.fm.intel.com with ESMTP; 02 Jun 2021 17:40:39 -0700 Cc: baolu.lu@linux.intel.com, iommu@lists.linux-foundation.org, linuxarm@huawei.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 0/7] iommu: Allow IOVA rcache range be configured To: John Garry , joro@8bytes.org, will@kernel.org, robin.murphy@arm.com References: <1622557781-211697-1-git-send-email-john.garry@huawei.com> <834ad35a-7310-1738-7d17-7c061ca73e4c@linux.intel.com> <1cbf8cc2-8cee-0579-2514-56f664baa9cd@huawei.com> From: Lu Baolu Message-ID: <5e6ff4d6-cd67-d4ab-814c-e10a258191b1@linux.intel.com> Date: Thu, 3 Jun 2021 08:39:29 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <1cbf8cc2-8cee-0579-2514-56f664baa9cd@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 6/2/21 3:48 PM, John Garry wrote: > On 02/06/2021 05:37, Lu Baolu wrote: >> On 6/1/21 10:29 PM, John Garry wrote: >>> For streaming DMA mappings involving an IOMMU and whose IOVA len >>> regularly >>> exceeds the IOVA rcache upper limit (meaning that they are not cached), >>> performance can be reduced. >>> >>> This is much more pronounced from commit 4e89dce72521 ("iommu/iova: >>> Retry >>> from last rb tree node if iova search fails"), as discussed at [0]. >>> >>> IOVAs which cannot be cached are highly involved in the IOVA ageing >>> issue, >>> as discussed at [1]. >>> >>> This series allows the IOVA rcache range be configured, so that we may >>> cache all IOVAs per domain, thus improving performance. >>> >>> A new IOMMU group sysfs file is added - max_opt_dma_size - which is used >>> indirectly to configure the IOVA rcache range: >>> /sys/kernel/iommu_groups/X/max_opt_dma_size >>> >>> This file is updated same as how the IOMMU group default domain type is >>> updated, i.e. must unbind the only device in the group first. >> >> Could you explain why it requires singleton group and driver unbinding >> if the user only wants to increase the upper limit? I haven't dived into >> the details yet, sorry if this is a silly question. > > Hi Baolu, > > I did actually try increasing the range for a 'live' domain in the v1 > series, but it turned out too messy. First problem is reallocating the > memory to hold the rcaches. Second problem is that we need to deal with > the issue that all IOVAs in the rcache need to be a pow-of-2, which is > difficult to enforce for IOVAs which weren't being cached before, but > now would be. > > So now I changed to work similar to how we change the default domain > type, i.e. don't operate on a 'live' domain. If these hard restrictions on users are just to walk around the messy code in kernel, I would rather solve those messy code to achieve a better user experience. :-) Best regards, baolu 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=-5.9 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 AAE7DC4708F for ; Thu, 3 Jun 2021 00:40:51 +0000 (UTC) Received: from smtp1.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 5C316613E6 for ; Thu, 3 Jun 2021 00:40:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5C316613E6 Authentication-Results: mail.kernel.org; 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d="scan'208";a="633512059" Received: from allen-box.sh.intel.com (HELO [10.239.159.105]) ([10.239.159.105]) by fmsmga006.fm.intel.com with ESMTP; 02 Jun 2021 17:40:39 -0700 Subject: Re: [PATCH v3 0/7] iommu: Allow IOVA rcache range be configured To: John Garry , joro@8bytes.org, will@kernel.org, robin.murphy@arm.com References: <1622557781-211697-1-git-send-email-john.garry@huawei.com> <834ad35a-7310-1738-7d17-7c061ca73e4c@linux.intel.com> <1cbf8cc2-8cee-0579-2514-56f664baa9cd@huawei.com> From: Lu Baolu Message-ID: <5e6ff4d6-cd67-d4ab-814c-e10a258191b1@linux.intel.com> Date: Thu, 3 Jun 2021 08:39:29 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <1cbf8cc2-8cee-0579-2514-56f664baa9cd@huawei.com> Content-Language: en-US Cc: linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, linuxarm@huawei.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-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Errors-To: iommu-bounces@lists.linux-foundation.org Sender: "iommu" On 6/2/21 3:48 PM, John Garry wrote: > On 02/06/2021 05:37, Lu Baolu wrote: >> On 6/1/21 10:29 PM, John Garry wrote: >>> For streaming DMA mappings involving an IOMMU and whose IOVA len >>> regularly >>> exceeds the IOVA rcache upper limit (meaning that they are not cached), >>> performance can be reduced. >>> >>> This is much more pronounced from commit 4e89dce72521 ("iommu/iova: >>> Retry >>> from last rb tree node if iova search fails"), as discussed at [0]. >>> >>> IOVAs which cannot be cached are highly involved in the IOVA ageing >>> issue, >>> as discussed at [1]. >>> >>> This series allows the IOVA rcache range be configured, so that we may >>> cache all IOVAs per domain, thus improving performance. >>> >>> A new IOMMU group sysfs file is added - max_opt_dma_size - which is used >>> indirectly to configure the IOVA rcache range: >>> /sys/kernel/iommu_groups/X/max_opt_dma_size >>> >>> This file is updated same as how the IOMMU group default domain type is >>> updated, i.e. must unbind the only device in the group first. >> >> Could you explain why it requires singleton group and driver unbinding >> if the user only wants to increase the upper limit? I haven't dived into >> the details yet, sorry if this is a silly question. > > Hi Baolu, > > I did actually try increasing the range for a 'live' domain in the v1 > series, but it turned out too messy. First problem is reallocating the > memory to hold the rcaches. Second problem is that we need to deal with > the issue that all IOVAs in the rcache need to be a pow-of-2, which is > difficult to enforce for IOVAs which weren't being cached before, but > now would be. > > So now I changed to work similar to how we change the default domain > type, i.e. don't operate on a 'live' domain. If these hard restrictions on users are just to walk around the messy code in kernel, I would rather solve those messy code to achieve a better user experience. :-) Best regards, baolu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu