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
This patch set enables vhost dequeue zero copy. The majority work goes
to patch 4: "vhost: add dequeue zero copy".
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).
---
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 | 11 ++
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 | 192 +++++++++++++++++---
10 files changed, 543 insertions(+), 162 deletions(-)
--
1.9.0
