[dpdk-dev] [PATCH 0/2] add lock-free mode for l3fwd

[Honnappa Nagarahalli]

> >
> > <snip>
> >
> > > >
> > > > Hi,
> > > >
> > > > >
> > > > > Lock-free mode is supported by hash library and LPM library.
> > > > > Now we add an option for l3fwd example to enable the lock-free
> mode.
> > > > > Necessary preparation steps are added to use lock-free LPM mode.
> > > >
> > > > Can I ask about the purpose of these changes?
> > > > Right now in  l3fwd both lpm and hash tables are static and hard-coded.
> > > > we initialize them at startup and then just do read from them.
> > > > Do you plan to enhance l3fwd with ability to dynamically update
> > > > tables contents?
> > > > Though fir that we first have to get rid of hard-coded values
> > > > (config file or
> > > so).
> > > > Konstantin
> > > >
> > > Thanks for your questions.
> > > Currently, we have no plan to enhance l3fwd with ability to
> > > dynamically update table contents.
> > > Lock-free method is being integrated into Hash library and LPM
> > > library.  Lock- free algorithms are not only about control plane
> > > (adding or deleting routes), they affect the data path performance as well.
> > > Since l3fwd application is showcasing data path performance, we need
> > > to show the impact of including the quiescent state reporting on data
> path.
> > > This change also serves as an example of using the RCU APIs.
> > >
> > Without the dynamic deletes the quiescent state reporting overhead is
> > not captured completely.
> > I suggest that we add and delete a small set of unrelated routes (the
> > routes that are not used currently) on a regular basis.
> >
> Add and delete unrelated routes on a regular basis will simulate overhead on
> control path. However, control path performance is not a l3fwd showcase,
> and it is covered by LPM performance unit test.
> On data path, quiescent state reporting overhead is constant (calling of
> rte_rcu_qsbr_quiescent).
> It will not be impacted by route addition / deletion.
The recent changes to RCU [1] are such that the reader threads avoid a write if there are no deletes. So, without the deletion, the impact on readers is complete.

[1] https://patchwork.dpdk.org/patch/58961/
> 
> > > > >
> > > > > Patch 2/2 has dependency on RCU QSBR integration with LPM library:
> > > > > http://patches.dpdk.org/project/dpdk/list/?series=6288
> > > > >
> > > > >
> > > > > Ruifeng Wang (2):
> > > > >   examples/l3fwd: add lock-free option for l3fwd
> > > > >   examples/l3fwd: integrate RCU QSBR for LPM mode
> > > > >
> > > > >  doc/guides/sample_app_ug/l3_forward.rst |  3 ++
> > > > >  examples/l3fwd/Makefile                 |  1 +
> > > > >  examples/l3fwd/l3fwd.h                  |  4 +-
> > > > >  examples/l3fwd/l3fwd_em.c               | 10 +++-
> > > > >  examples/l3fwd/l3fwd_lpm.c              | 72
> > +++++++++++++++++++++++--
> > > > >  examples/l3fwd/main.c                   | 27 ++++++++--
> > > > >  examples/l3fwd/meson.build              |  1 +
> > > > >  7 files changed, 108 insertions(+), 10 deletions(-)
> > > > >
> > > > > --
> > > > > 2.17.1
> > >
> >
>