Hi, I have question about RX merge feature. Below mentions that set mrg_rxbuf=off can improve performance. So question 1: How much would it be affected for throughput?
********************* Rx Mergeable Buffers¶<http://docs.openvswitch.org/en/latest/intro/install/dpdk/?highlight=mrg_rxbuf#rx-mergeable-buffers> Rx mergeable buffers is a virtio feature that allows chaining of multiple virtio descriptors to handle large packet sizes. Large packets are handled by reserving and chaining multiple free descriptors together. Mergeable buffer support is negotiated between the virtio driver and virtio device and is supported by the DPDK vhost library. This behavior is supported and enabled by default, however in the case where the user knows that rx mergeable buffers are not needed i.e. jumbo frames are not needed, it can be forced off by adding mrg_rxbuf=off to the QEMU command line options. By not reserving multiple chains of descriptors it will make more individual virtio descriptors available for rx to the guest using dpdkvhost ports and this can improve performance. *********************** http://docs.openvswitch.org/en/latest/howto/dpdk/?highlight=mrg_rxbuf It mentions mrg_rxbuf must be set to on in order to support Jumbo frames. So question 2: I am wondering if I set mtu to 2000, should mrg_rxbuf be also a MUST? Is there a threshold to switch the configuration? ************************ Some additional configuration is needed to take advantage of jumbo frames with vHost ports: mergeable buffers must be enabled for vHost ports, as demonstrated in the QEMU command line snippet below:”. ****************************** BR, Zhike
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