This is a basic implementation of packed virtqueues as specified in the Virtio 1.1 draft. A compiled version of the current draft is available at https://github.com/oasis-tcs/virtio-docs.git (or as .pdf at https://github.com/oasis-tcs/virtio-docs/blob/master/virtio-v1.1-packed-wd10.pdf
It does not implement yet indirect descriptors and checksum offloading. A packed virtqueue is different from a split virtqueue in that it consists of only a single descriptor ring that replaces available and used ring, index and descriptor buffer. Each descriptor is readable and writable and has a flags field. These flags will mark if a descriptor is available or used. To detect new available descriptors even after the ring has wrapped, device and driver each have a single-bit wrap counter that is flipped from 0 to 1 and vice versa every time the last descriptor in the ring is used/made available. The idea behind this is to 1. improve performance by avoiding cache misses and 2. be easier for devices to implement. Regarding performance: with these patches I get 21.13 Mpps on my system as compared to 18.8 Mpps with the virtio 1.0 code. Packet size was 64 bytes, 0.05% acceptable loss. Test setup is described as in http://dpdk.org/doc/guides/howto/pvp_reference_benchmark.html Packet generator: MoonGen Intel(R) Xeon(R) CPU E5-2665 0 @ 2.40GHz Intel X710 NIC RHEL 7.4 Device under test: Intel(R) Xeon(R) CPU E5-2667 v4 @ 3.20GHz Intel X710 NIC RHEL 7.4 VM on DuT: RHEL7.4 I plan to do more performance test with bigger frame sizes. This patch series is based on a prototype implemented by Yuanhan Liu and Tiwei Bie. changes from v3->v4: * added helpers to increment index and set available/used flags * driver keeps track of number of descriptors used * change logic in set_rxtx_funcs() * add patch for ctrl virtqueue with support for packed virtqueues * rename virtio-1.1.h to virtio-packed.h * fix wrong sizeof() in "vhost: vring address setup for packed queues" * fix coding style of function definition in "net/virtio: add packed virtqueue helpers" * fix padding in vring_size() * move patches to enable packed virtqueues end of series * v4 has two open problems: I'm sending it out anyway for feedback/help: * when VIRTIO_NET_F_MRG_RXBUF enabled only 128 packets are send in guest, i.e. when ring is full for the first time. I suspect a bug in setting the avail/used flags changes from v2->v3: * implement event suppression * add code do dump packed virtqueues * don't use assert in vhost code * rename virtio-user parameter to packed-vq * support rxvf flush changes from v1->v2: * don't use VIRTQ_DESC_F_NEXT in used descriptors (Jason) * no rte_panice() in guest triggerable code (Maxime) * use unlikely when checking for vq (Maxime) * rename everything from _1_1 to _packed (Yuanhan) * add two more patches to implement mergeable receive buffers Jens Freimann (16): net/virtio: vring init for packed queues net/virtio: add virtio 1.1 defines net/virtio: add packed virtqueue helpers net/virtio: flush packed receive virtqueues net/virtio: dump packed virtqueue data net/virtio: implement transmit path for packed queues net/virtio: add virtio send command packed queue support net/virtio: add support for mergeable buffers with packed virtqueues net/virtio: add support for event suppression vhost: add virtio packed virtqueue defines vhost: add helpers for packed virtqueues vhost: dequeue for packed queues vhost: packed queue enqueue path vhost: add support for mergeable buffers with packed virtqueues vhost: add event suppression for packed queues net/virtio: by default disable packed virtqueues Yuanhan Liu (4): net/virtio-user: add option to use packed queues net/virtio: implement receive path for packed queues vhost: vring address setup for packed queues vhost: by default disable packed virtqueues config/common_base | 2 + drivers/net/virtio/virtio_ethdev.c | 127 +++++- drivers/net/virtio/virtio_ethdev.h | 5 + drivers/net/virtio/virtio_pci.h | 8 + drivers/net/virtio/virtio_ring.h | 97 ++++- drivers/net/virtio/virtio_rxtx.c | 357 +++++++++++++++- drivers/net/virtio/virtio_user/virtio_user_dev.c | 6 +- drivers/net/virtio/virtio_user/virtio_user_dev.h | 3 +- drivers/net/virtio/virtio_user_ethdev.c | 15 +- drivers/net/virtio/virtqueue.c | 16 + drivers/net/virtio/virtqueue.h | 113 ++++- lib/librte_vhost/socket.c | 5 + lib/librte_vhost/vhost.c | 16 + lib/librte_vhost/vhost.h | 70 +++- lib/librte_vhost/vhost_user.c | 45 +- lib/librte_vhost/virtio-packed.h | 86 ++++ lib/librte_vhost/virtio_net.c | 503 +++++++++++++++++++++-- 17 files changed, 1398 insertions(+), 76 deletions(-) create mode 100644 lib/librte_vhost/virtio-packed.h -- 2.14.3