On Wed, Jun 28, 2023 at 11:46:22AM +0800, Jason Wang wrote: > On Wed, Jun 28, 2023 at 12:35 AM Heng Qi <[email protected]> wrote: > > > > 1. Currently, a received encapsulated packet has an outer and an inner > > header, but > > the virtio device is unable to calculate the hash for the inner header. The > > same > > flow can traverse through different tunnels, resulting in the encapsulated > > packets being spread across multiple receive queues (refer to the figure > > below). > > However, in certain scenarios, we may need to direct these encapsulated > > packets of > > the same flow to a single receive queue. This facilitates the processing > > of the flow by the same CPU to improve performance (warm caches, less > > locking, etc.). > > > > client1 client2 > > | +-------+ | > > +------->|tunnels|<--------+ > > +-------+ > > | | > > v v > > +-----------------+ > > | monitoring host | > > +-----------------+ > > > > To achieve this, the device can calculate a symmetric hash based on the > > inner headers > > of the same flow. > > > > 2. For legacy systems, they may lack entropy fields which modern protocols > > have in > > the outer header, resulting in multiple flows with the same outer header but > > different inner headers being directed to the same receive queue. This > > results in > > poor receive performance. > > > > To address this limitation, inner header hash can be used to enable the > > device to advertise > > the capability to calculate the hash for the inner packet, regaining better > > receive performance. > > > > Fixes: https://github.com/oasis-tcs/virtio-spec/issues/173 > > Signed-off-by: Heng Qi <[email protected]> > > Reviewed-by: Xuan Zhuo <[email protected]> > > Reviewed-by: Parav Pandit <[email protected]> > > --- > > v18->v19: > > 1. Have a single structure instead of two. @Michael S . Tsirkin > > 2. Some small rewrites. @Michael S . Tsirkin > > 3. Rebase to master. > > > > v17->v18: > > 1. Some rewording suggestions from Michael (Thanks!). > > 2. Use 0 to disable inner header hash and remove > > VIRTIO_NET_HASH_TUNNEL_TYPE_NONE. > > v16->v17: > > 1. Some small rewrites. @Parav Pandit > > 2. Add Parav's Reviewed-by tag (Thanks!). > > > > v15->v16: > > 1. Remove the hash_option. In order to delimit the inner header > > hash and RSS > > configuration, the ability to configure the outer src udp port > > hash is given > > to RSS. This is orthogonal to inner header hash, which will be > > done in the > > RSS capability extension topic (considered as an RSS extension > > together > > with the symmetric toeplitz hash algorithm, etc.). @Parav Pandit > > @Michael S . Tsirkin > > 2. Fix a 'field' typo. @Parav Pandit > > > > v14->v15: > > 1. Add tunnel hash option suggested by @Michael S . Tsirkin > > 2. Adjust some descriptions. > > > > v13->v14: > > 1. Move supported_hash_tunnel_types from config space into cvq > > command. @Parav Pandit > > I may miss some discussions, but this complicates the provisioning a lot. > > Having it in the config space, then a type agnostic provisioning > through config space + feature bits just works fine. > > If we move it only via cvq, we need device specific provisioning interface. > > Thanks
Yea that's what I said too. Debugging too. I think we should build a consistent solution that allows accessing config space through DMA, separately from this effort. Parav do you think you can live with this approach so this specific proposal can move forward? -- MST --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
