Re: [dpdk-dev] [PATCH] vhost: optimize vhost memcpy

["Wang, Zhihong" <zhihong.wang@intel.com>]

> -----Original Message-----
> From: Yuanhan Liu [mailto:yuanhan.liu@linux.intel.com]
> Sent: Monday, December 5, 2016 6:37 PM
> To: Wang, Zhihong <zhihong.wang@intel.com>
> Cc: dev@dpdk.org; Thomas Monjalon <thomas.monjalon@6wind.com>
> Subject: Re: [PATCH] vhost: optimize vhost memcpy
> 
> 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.

Yes I agree this is a better way to introduce this patch, I'll send out v2.

> 
> 	--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