Re: [dpdk-dev] [PATCH v2] config: enable packet data prefetch

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

<snip>

> >
> > 23/09/2020 03:51, Marvin Liu:
> > > Data prefetch instruction can preload data into cpu’s hierarchical
> > > cache before data access. Virtualized data paths like virtio
> > > utilized this feature for acceleration. Since most modern cpus have
> > > support prefetch function, we can enable packet data prefetch as default.
> > >
> > > Signed-off-by: Marvin Liu <yong.liu@intel.com>
> > > ---
> > > +#define RTE_PMD_PACKET_PREFETCH 1
> >
> > We could also remove the related #ifdefs.
> >
> > What can be the drawback of always enable those prefetches?
> >
> 
> Hi Thomas,
> I think the potential drawback is that current prefetch location cannot
> guarantee the best performance across different platforms.
Then, does it make sense to enable this by default?

> Each developer has tuned the performance by adding prefetch instruction
> and verified the result on himself platform.
> So prefetch location is based on certain platform, also it will be hard for
> developer to compare the results across platforms.
> 
> Thanks,
> Marvin