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d="scan'208";a="633098715" Received: from allen-box.sh.intel.com (HELO [10.239.159.105]) ([10.239.159.105]) by fmsmga006.fm.intel.com with ESMTP; 01 Jun 2021 21:38:34 -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> From: Lu Baolu Message-ID: <834ad35a-7310-1738-7d17-7c061ca73e4c@linux.intel.com> Date: Wed, 2 Jun 2021 12:37:20 +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: <1622557781-211697-1-git-send-email-john.garry@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 6/1/21 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. Best regards, baolu _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu