On 08/23/2016 10:10 AM, Yuanhan Liu wrote: > This patch set enables vhost Tx zero copy. The majority work goes to > patch 4: vhost: add Tx zero copy. > > The basic idea of Tx 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_TX_ZERO_COPY, to enable > Tx zero copy, which is disabled by default. > > Few more TODOs are left, including handling a desc buf that is across > two physical pages, updating release note, etc. Those will be fixed > in later version. For now, here is a simple one that hopefully it > shows the idea clearly. > > I did some quick tests, the performance gain is quite impressive. > > For a simple dequeue workload (running rxonly in vhost-pmd and runnin > txonly in guest testpmd), it yields 40+% performance boost for packet > size 1400B. > > For VM2VM iperf test case, it's even better: about 70% boost.
This is indeed impressive. Somewhere else, you mention that there is a small regression with small packets. Do you have some figures to share? Also, with this feature OFF, do you see some regressions for both small and bigger packets? Thanks, Maxime > > --- > Yuanhan Liu (6): > vhost: simplify memory regions handling > vhost: get guest/host physical address mappings > vhost: introduce last avail idx for Tx > vhost: add Tx zero copy > vhost: add a flag to enable Tx zero copy > examples/vhost: add an option to enable Tx zero copy > > doc/guides/prog_guide/vhost_lib.rst | 7 +- > 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 | 103 +++++++++---- > lib/librte_vhost/vhost_user.c | 297 > +++++++++++++++++++++++------------- > lib/librte_vhost/virtio_net.c | 188 +++++++++++++++++++---- > 8 files changed, 472 insertions(+), 160 deletions(-) >
