Re: [dpdk-dev] [PATCH v7 4/5] hash: add lock-free read-write concurrency

[Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>]

> 
> > > Agree. There are multiple micro-architectures in Arm eco-system. We
> > should establish few simple rules to make sure algorithms perform well
> > on all the available platforms. I established few rules in VPP and
> > they are working fine so far.
> >
> > Can you share that rules for everyone's benefit?
> >
> These are just few simple rules anyone can think of, but avoid the surprises.
> We identified a owner for each platform (we have this already in DPDK, even
> across platforms) Each patch submitted for Arm platforms is marked with -2
> (VPP uses Gerrit) Every platform owner tests on her/his platform. -2 will be
> removed only if it does not cause regression on any platforms. Platform
> owner helps out with optimization where required as they understand their
> micro-architecture best. I guess this is what is supposed to happen through
> the review process in DPDK. But making sure everyone tests it before it gets
> merged avoids the surprises.
> 
> > > >
> > > > IMO, This scheme won't work. I think, we are introducing such
> > > > performance critical feature, we need to put under function
> > > > pointer scheme so that if an application does not need such
> > > > feature it can use
> > plain loads.
> > > >
> > > IMO, we should do some more debugging before going into exploring
> > > other
> > options.
> >
> > Yes. But, how do we align with v18.11 release?
> >
> I think I have spent enough time optimizing the code. Please provide the
> feedback and I will work on completing the fix.
> 
> However, if the new patch is not satisfactory enough, we need another plan.
> 
> You had mentioned about using function pointers. I suggest, we use the
> function pointer only for lookup function. Otherwise, it will be too much of
> code duplication.
> When lock-free is not used, the function with no memory-orderings will be
> called. However, I am not sure about the function pointer overhead. But this
> will be a simple change.
Yipeng/Bruce, would this work for you?