This series introduces an optimization for vsock/virtio to reduce latency and increase the throughput: When the guest sends a packet to the host, and the intermediate queue (send_pkt_queue) is empty, if there is enough space, the packet is put directly in the virtqueue. v3->v4 While running experiments on fio with 64B payload, I realized that there was a mistake in my fio configuration, so I re-ran all the experiments and now the latency numbers are indeed lower with the patch applied. I also noticed that I was kicking the host without the lock. - Fixed a configuration mistake on fio and re-ran all experiments. - Fio latency measurement using 64B payload. - virtio_transport_send_skb_fast_path sends kick with the tx_lock acquired - Addressed all minor style changes requested by maintainer. - Rebased on latest net-next - Link to v3: https://lore.kernel.org/r/20240711-pinna-v3-0-697d4164fe80@xxxxxxxxxxx v2->v3 - Performed more experiments using iperf3 using multiple streams - Handling of reply packets removed from virtio_transport_send_skb, as is needed just by the worker. - Removed atomic_inc/atomic_sub when queuing directly to the vq. - Introduced virtio_transport_send_skb_fast_path that handles the steps for sending on the vq. - Fixed a missing mutex_unlock in error path. - Changed authorship of the second commit - Rebased on latest net-next v1->v2 In this v2 I replaced a mutex_lock with a mutex_trylock because it was insidea RCU critical section. I also added a check on tx_run, so if the module is being removed the packet is not queued. I'd like to thank Stefano for reporting the tx_run issue. Applied all Stefano's suggestions: - Minor code style changes - Minor commit text rewrite Performed more experiments: - Check if all the packets go directly to the vq (Matias' suggestion) - Used iperf3 to see if there is any improvement in overall throughput from guest to host - Pinned the vhost process to a pCPU. - Run fio using 512B payload Rebased on latest net-next --- Luigi Leonardi (1): vsock/virtio: avoid queuing packets when intermediate queue is empty Marco Pinna (1): vsock/virtio: refactor virtio_transport_send_pkt_work net/vmw_vsock/virtio_transport.c | 144 +++++++++++++++++++++++++-------------- 1 file changed, 94 insertions(+), 50 deletions(-) --- base-commit: 1722389b0d863056d78287a120a1d6cadb8d4f7b change-id: 20240730-pinna-db8cc1b8b037 Best regards, -- Luigi Leonardi <luigi.leonardi@xxxxxxxxxxx>
