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d="scan'208";a="16366027" Date: Tue, 28 Apr 2020 09:07:24 +0200 From: Roger Pau =?utf-8?B?TW9ubsOp?= To: tosher 1 Subject: Re: Xen network domain performance for 10Gb NIC Message-ID: <20200428070724.GS28601@Air-de-Roger> References: <1359850718.562651.1587928713792.ref@mail.yahoo.com> <1359850718.562651.1587928713792@mail.yahoo.com> <20200427070317.GL28601@Air-de-Roger> <1693679742.27711.1588051435928@mail.yahoo.com> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Disposition: inline In-Reply-To: <1693679742.27711.1588051435928@mail.yahoo.com> X-ClientProxiedBy: AMSPEX02CAS02.citrite.net (10.69.22.113) To AMSPEX02CL02.citrite.net (10.69.22.126) X-BeenThere: xen-devel@lists.xenproject.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Cc: Xen-devel Errors-To: xen-devel-bounces@lists.xenproject.org Sender: "Xen-devel" On Tue, Apr 28, 2020 at 05:23:55AM +0000, tosher 1 wrote: > > Driver domains with passthrough devices need to perform IOMMU > operations in order to add/remove page table entries when doing grant > maps (ie: IOMMU TLB flushes), while dom0 doesn't need to because it > has the whole RAM identity mapped in the IOMMU tables. Depending on > how fast your IOMMU is and what capabilities it has doing such > operations can introduce a significant amount of overhead. > > It makes sense to me. Do you know, in general, how to measure IOMMU performance, and what features/properties of IOMMU can contribute to getting a better network throughput? Please let me know. Hm, not really. You would have to modify Xen and/or the Linux kernel in order to time the IOMMU or the grant map operations in order to get an idea. Do you get the expected performance from the driver domain when not using it as a backend? Ie: running the iperf benchmarks directly on the driver domain and not on the guest. Roger.