Re: [dpdk-dev] [dpdk-stable] [PATCH v5 2/2] ring: move the atomic load of head above the loop

[Thomas Monjalon <thomas@monjalon.net>]

03/11/2018 10:34, Honnappa Nagarahalli:
> > > > ---
> > > >  doc/guides/rel_notes/release_18_11.rst |  7 +++++++
> > > >  lib/librte_ring/rte_ring_c11_mem.h     | 10 ++++------
> > > >  2 files changed, 11 insertions(+), 6 deletions(-)
> > > >
> > > > diff --git a/doc/guides/rel_notes/release_18_11.rst
> > > > b/doc/guides/rel_notes/release_18_11.rst
> > > > index 376128f..b68afab 100644
> > > > --- a/doc/guides/rel_notes/release_18_11.rst
> > > > +++ b/doc/guides/rel_notes/release_18_11.rst
> > > > @@ -69,6 +69,13 @@ New Features
> > > >    checked out against that dma mask and rejected if out of range.
> > > > If more
> > > than
> > > >    one device has addressing limitations, the dma mask is the more
> > > restricted one.
> > > >
> > > > +* **Updated the ring library with C11 memory model.**
> > > > +
> > > > +  Updated the ring library with C11 memory model, in our tests the
> > > > + changes  decreased latency by 27~29% and 3~15% for MPMC and SPSC
> > > cases respectively.
> > > > +  The real improvements may vary with the number of contending
> > > > + lcores and the  size of ring.
> > > > +
> > > Is this a little misleading, and will users expect massive performance
> > > improvements generally? The C11 model seems to be used only on some,
> > > but not all, arm platforms, and then only with "make" builds.
> > >
> > > config/arm/meson.build: ['RTE_USE_C11_MEM_MODEL', false]]
> This is an error. There is already an agreement that on Arm based platforms, C11 memory model would be used by default. Specific platforms can override it if required.
> Would this be ab acceptable change for RC2 or RC3?

If NXP and Cavium agrees, I think it can go in RC2.
For RC3, not sure.