[dpdk-dev] [PATCH v5 0/7] virtio ring layout optimization and simple rx/tx processing
Tan, Jianfeng
jianfeng.tan at intel.com
Tue Oct 27 02:44:09 CET 2015
> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Huawei Xie
> Sent: Sunday, October 25, 2015 11:35 PM
> To: dev at dpdk.org
> Subject: [dpdk-dev] [PATCH v5 0/7] virtio ring layout optimization and simple
> rx/tx processing
>
> Changes in v5:
> - Call __rte_pktmbuf_prefree_seg to check refcnt when free mbufs
>
> Changes in v4:
> - Fix the error in virtio tx ring layout ascii chart in the commit message
> - Move virtio_xmit_cleanup ahead to free descriptors earlier
> - Test merge-able feature when select simple rx/tx functions
>
> Changes in v3:
> - Remove unnecessary NULL test for rte_free
> - Remove unnecessary assign of local var after free
> - Remove return at the end of void function
> - Remove always_inline attribute for virtio_xmit_cleanup
> - Reword some commit messages
> - Add TODO in the commit message of simple tx patch
>
> Changes in v2:
> - Remove the configure macro
> - Enable simple R/TX processing when user specifies simple txq flags
> - Reword some comments and commit messages
>
> In DPDK based switching enviroment, mostly vhost runs on a dedicated core
> while virtio processing in guest VMs runs on other different cores.
> Take RX for example, with generic implementation, for each guest buffer,
> a) virtio driver allocates a descriptor from free descriptor list
> b) modify the entry of avail ring to point to allocated descriptor
> c) after packet is received, free the descriptor
>
> When vhost fetches the avail ring, it need to fetch the modified L1 cache
> from virtio core, which is a heavy cost in current CPU implementation.
>
> This idea of this optimization is:
> allocate the fixed descriptor for each entry of avail ring, so avail ring will
> always be the same during the run.
> This removes L1M cache transfer from virtio core to vhost core for avail ring.
> (Note we couldn't avoid the cache transfer for descriptors).
> Besides, descriptor allocation and free operation is eliminated.
> This also makes vector procesing possible to further accelerate the
> processing.
>
> This is the layout for the avail ring(take 256 ring entries for example), with
> each entry pointing to the descriptor with the same index.
> avail
> idx
> +
> |
> +----+----+---+-------------+------+
> | 0 | 1 | 2 | ... | 254 | 255 | avail ring
> +-+--+-+--+-+-+---------+---+--+---+
> | | | | | |
> | | | | | |
> v v v | v v
> +-+--+-+--+-+-+---------+---+--+---+
> | 0 | 1 | 2 | ... | 254 | 255 | desc ring
> +----+----+---+-------------+------+
> |
> |
> +----+----+---+-------------+------+
> | 0 | 1 | 2 | | 254 | 255 | used ring
> +----+----+---+-------------+------+
> |
> +
>
> This is the ring layout for TX.
> As we need one virtio header for each xmit packet, we have 128 slots
> available.
>
> ++
> ||
> ||
> +-----+-----+-----+--------------+------+------+------+
> | 0 | 1 | ... | 127 || 128 | 129 | ... | 255 | avail ring
> +--+--+--+--+-----+---+------+---+--+---+------+--+---+
> | | | || | | |
> v v v || v v v
> +--+--+--+--+-----+---+------+---+--+---+------+--+---+
> | 127 | 128 | ... | 255 || 127 | 128 | ... | 255 | desc ring for virtio_net_hdr
> +--+--+--+--+-----+---+------+---+--+---+------+--+---+
> | | | || | | |
> v v v || v v v
> +--+--+--+--+-----+---+------+---+--+---+------+--+---+
> | 0 | 1 | ... | 127 || 0 | 1 | ... | 127 | desc ring for tx dat
> +-----+-----+-----+--------------+------+------+------+
> ||
> ||
> ++
>
>
> Performance boost could be observed only if the virtio backend isn't the
> bottleneck or in VM2VM case.
> There are also several vhost optimization patches to be submitted later.
>
>
> Huawei Xie (7):
> virtio: add virtio_rxtx.h header file
> virtio: add software rx ring, fake_buf into virtqueue
> virtio: rx/tx ring layout optimization
> virtio: fill RX avail ring with blank mbufs
> virtio: virtio vec rx
> virtio: simple tx routine
> virtio: pick simple rx/tx func
>
> drivers/net/virtio/Makefile | 2 +-
> drivers/net/virtio/virtio_ethdev.c | 12 +-
> drivers/net/virtio/virtio_ethdev.h | 5 +
> drivers/net/virtio/virtio_rxtx.c | 56 ++++-
> drivers/net/virtio/virtio_rxtx.h | 39 +++
> drivers/net/virtio/virtio_rxtx_simple.c | 414
> ++++++++++++++++++++++++++++++++
> drivers/net/virtio/virtqueue.h | 5 +
> 7 files changed, 529 insertions(+), 4 deletions(-) create mode 100644
> drivers/net/virtio/virtio_rxtx.h create mode 100644
> drivers/net/virtio/virtio_rxtx_simple.c
>
> --
> 1.8.1.4
Acked-by Jianfeng Tan <jianfeng.tan at intel.com>
Thanks,
Jianfeng
More information about the dev
mailing list