Indirect desc #4734
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Indirect desc #4734
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VIRTIO_RING_F_INDIRECT_DESC is declared in the virtio_ring.h, so modify bindgen to parse all `VIRTIO_RING_` constants. Signed-off-by: Egor Lazarchuk <[email protected]>
Now IoVecBuffer/Mut can be built from descriptor chains utilizing VIRTQ_DESC_F_INDIRECT flag. The way indirect descriptors work is: - Descriptors from descriptor table instead of pointing to the buffers where data needs to be written to/read from now can point to buffers that contain other descriptor table. That 'indirect' descriptor table contains descriptor which point to actual buffers for data. - All descriptor in the 'indirect' descriptor table are processed sequentially. - The `VIRTQ_DESC_F_WRITE` flag is ignored for the main descriptor (the one from original descriptor table) Signed-off-by: Egor Lazarchuk <[email protected]>
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After doing performance testing there is no impact from indirect descriptors, closing. |
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Changes
Add support for
INDIRECT_DESCforIoVecBuff/Mutand enabledVIRTIO_RING_F_INDIRECT_DESCflag forvirtio-netdevice. This feature allows guest to create more buffers for packets which in turn should help with throughput when all available descriptors are used.Note that indirect descriptors can only be enabled for TX queue. This is a linux virtio-net driver behavior.
Reason
Should help with network performance.
Note
This PR is built on top of #4658, so needs to be merged after it.
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rust-vmm.