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

Ruifeng Wang (Arm Technology China) Ruifeng.Wang at arm.com
Tue Sep 10 11:56:33 CEST 2019


> -----Original Message-----
> From: Ananyev, Konstantin <konstantin.ananyev at intel.com>
> Sent: Tuesday, September 10, 2019 17:06
> To: Ruifeng Wang (Arm Technology China) <Ruifeng.Wang at arm.com>;
> Kantecki, Tomasz <tomasz.kantecki at intel.com>
> Cc: dev at dpdk.org; Gavin Hu (Arm Technology China) <Gavin.Hu at arm.com>;
> Honnappa Nagarahalli <Honnappa.Nagarahalli at arm.com>; nd
> <nd at arm.com>; nd <nd at arm.com>
> Subject: RE: [dpdk-dev] [PATCH 0/2] add lock-free mode for l3fwd
> 
> 
> 
> > >
> > > >
> > > > 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.
> 
> 
> But what you suggest doesn't provide the complete picture.
> With dynamic updates in place (via control path) the data-path impact might
> be completely different then without.
> Again without dynamic updates how can you test that your data-path lock-
> free approach does work as expected?
> Also it can't even be used as a reference implementation for users, as half of
> the functionality they need to implement is simply missing.
> My opinion - we either need to leave l3fwd as it is (static routes), or
> implement a proper control path with ability to dynamically update routes
> before starting to introduce some synchronization schemes (RCU or
> whatever).
> 
> Konstantin
> 

Agree that dynamic control path updates should be included for a whole picture.
I will add dynamic update to l3fwd and reroll the patch series.
Thanks.

> >
> > > >
> > > > 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



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