[dpdk-dev] [PATCH] net/memif: relax barrier for zero copy path

[Jakub Grajciar -X (jgrajcia - PANTHEON TECH SRO at Cisco)]

> > > >
> > > > Using 'rte_mb' to synchronize the shared ring head/tail between
> > > > producer and consumer will stall the pipeline and damage
> > > > performance on the weak memory model platforms, such like aarch64.
> > > >
> > > > Relax the expensive barrier with c11 atomic with explicit memory
> > > > ordering can improve 3.6% performance on throughput.
> >
> > My question here is: `rte_mb` is supposed to make sure that head/tail
> > pointer are not updated before the packets are written into shared
> memory.
> > Does the atomic ensures that the packets are written into shared
> > memory before head/tail pointers are updated?
> 
> Yes, it does.
> The atomic store-release acts as a one-way barrier here to make sure all the
> memory accesses before the store-release are observed before it.

Ok then, since the sync is there and the rest seems fine to me.

Thanks,
Jakub

Reviewed-by: Jakub Grajciar <jgrajcia at cisco.com>