Re: [PATCH] vhost: optimize vhost memcpy

[Yuanhan Liu <yuanhan.liu@linux.intel.com>]

On Mon, Dec 05, 2016 at 10:27:00AM +0000, Wang, Zhihong wrote:
> > I like this function a lot, since it's really simple and straightforward!
> > Moreover, it performs better.
> > 
> > But, I don't quite like how this function is proposed:
> > 
> > - rte_movX are more like internal help functions that should be used only
> >   in corresponding rte_memcpy.h file.
> > 
> > - It's a good optimization, however, it will not benefit for other use
> >   cases, though vhost is the most typical case here.
> > 
> > - The optimization proves to be good for X86, but think there is no
> >   guarantee it may behave well for other platforms, say ARM.
> > 
> > I still would suggest you to go this way: move this function into x86's
> > rte_memcpy.h and call it when the data is well aligned.
> 
> 
> Do you mean to add something like rte_memcpy_aligned() in 
> lib/librte_eal/common/include/generic/rte_memcpy.h?

Yes, but this one is not supposed to be exported as a public API.
It should be called inside rte_memcpy (when data is well aligned).
In this way, only rte_memcpy is exposed, and nothing else should
be changed.

	--yliu
> 
> I thought of this way before, and didn't choose it because it requires
> changes in eal. But it would be a clean solution, I'd certainly like
> to implement it this way if people are okay with it.
> 
> 
> Thanks
> Zhihong
> 
> 
> > 
> > 	--yliu