On Sun, Oct 09, 2016 at 03:27:53PM +0800, Yuanhan Liu wrote:
> This patch set enables vhost dequeue zero copy. The majority work goes
> to patch 4: "vhost: add dequeue zero copy".
Applied to dpdk-next-virtio.
--yliu
>
> The basic idea of dequeue zero copy is, instead of copying data from the
> desc buf, here we let the mbuf reference the desc buf addr directly.
>
> The major issue behind that is how and when to update the used ring.
> You could check the commit log of patch 4 for more details.
>
> Patch 5 introduces a new flag, RTE_VHOST_USER_DEQUEUE_ZERO_COPY, to enable
> dequeue zero copy, which is disabled by default.
>
> The performance gain is quite impressive. For a simple dequeue workload
> (running rxonly in vhost-pmd and runnin txonly in guest testpmd), it yields
> 50+% performance boost for packet size 1500B. For VM2VM iperf test case,
> it's even better: about 70% boost.
>
> For small packets, the performance is worse (it's expected, as the extra
> overhead introduced by zero copy outweighs the benefits from saving few
> bytes copy).
>
> v3: - rebase: mainly for removing conflicts with the Tx indirect patch
> - don't update last_used_idx twice for zero-copy mode
> - handle two mssiing "Tx -> dequeue" renames in log and usage
>
> v2: - renamed "tx zero copy" to "dequeue zero copy", to reduce confusions.
> - hnadle the case that a desc buf might across 2 host phys pages
> - use MAP_POPULATE to let kernel populate the page tables
> - updated release note
> - doc-ed the limitations for the vm2nic case
> - merge 2 continuous guest phys memory region
> - and few more trivial changes, please see them in the corresponding
> patches
>
> ---
> Yuanhan Liu (7):
> vhost: simplify memory regions handling
> vhost: get guest/host physical address mappings
> vhost: introduce last avail idx for dequeue
> vhost: add dequeue zero copy
> vhost: add a flag to enable dequeue zero copy
> examples/vhost: add an option to enable dequeue zero copy
> net/vhost: add an option to enable dequeue zero copy
>
> doc/guides/prog_guide/vhost_lib.rst | 35 +++-
> doc/guides/rel_notes/release_16_11.rst | 13 ++
> drivers/net/vhost/rte_eth_vhost.c | 13 ++
> examples/vhost/main.c | 19 +-
> lib/librte_vhost/rte_virtio_net.h | 1 +
> lib/librte_vhost/socket.c | 5 +
> lib/librte_vhost/vhost.c | 12 ++
> lib/librte_vhost/vhost.h | 102 ++++++++---
> lib/librte_vhost/vhost_user.c | 315
> ++++++++++++++++++++++-----------
> lib/librte_vhost/virtio_net.c | 196 +++++++++++++++++---
> 10 files changed, 549 insertions(+), 162 deletions(-)
>
> --
> 1.9.0
