On 2024/09/15 21:48, Stephen Hemminger wrote:
On Sun, 15 Sep 2024 10:17:39 +0900
Akihiko Odaki <akihiko.odaki@xxxxxxxxxx> wrote:
virtio-net have two usage of hashes: one is RSS and another is hash
reporting. Conventionally the hash calculation was done by the VMM.
However, computing the hash after the queue was chosen defeats the
purpose of RSS.
Another approach is to use eBPF steering program. This approach has
another downside: it cannot report the calculated hash due to the
restrictive nature of eBPF.
Introduce the code to compute hashes to the kernel in order to overcome
thse challenges.
An alternative solution is to extend the eBPF steering program so that it
will be able to report to the userspace, but it is based on context
rewrites, which is in feature freeze. We can adopt kfuncs, but they will
not be UAPIs. We opt to ioctl to align with other relevant UAPIs (KVM
and vhost_net).
This will be useful for DPDK. But there still are cases where custom
flow rules are needed. I.e the RSS happens after other TC rules.
It would be a good if skbedit supported RSS as an option.
Hi,
It is nice to hear about a use case other than QEMU or virtualization. I
implemented RSS as tuntap ioctl because:
- It is easier to configure for the user of tuntap (e.g., QEMU)
- It implements hash reporting, which is specific to tuntap.
You can still add skbedit if you want to override RSS for some packets
with filter. Please tell me if it is not sufficient for your use case.
Regards,
Akihiko Odaki
