[dpdk-dev] [PATCH v7 1/3] eal/x86: run-time dispatch over memcpy
konstantin.ananyev at intel.com
Fri Oct 13 09:31:21 CEST 2017
> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas at monjalon.net]
> Sent: Friday, October 13, 2017 8:22 AM
> To: Li, Xiaoyun <xiaoyun.li at intel.com>
> Cc: dev at dpdk.org; Ananyev, Konstantin <konstantin.ananyev at intel.com>; Richardson, Bruce <bruce.richardson at intel.com>; Lu, Wenzhuo
> <wenzhuo.lu at intel.com>; Zhang, Helin <helin.zhang at intel.com>
> Subject: Re: [dpdk-dev] [PATCH v7 1/3] eal/x86: run-time dispatch over memcpy
> 13/10/2017 03:06, Li, Xiaoyun:
> > Hi
> > Sorry for the late reply. I took AL last 3 days.
> > From: Thomas Monjalon [mailto:thomas at monjalon.net]
> > > 05/10/2017 14:33, Xiaoyun Li:
> > > > +/**
> > > > + * Macro for copying unaligned block from one location to another
> > > > +with constant load offset,
> > > > + * 47 bytes leftover maximum,
> > > > + * locations should not overlap.
> > > > + * Requirements:
> > > > + * - Store is aligned
> > > > + * - Load offset is <offset>, which must be immediate value within
> > > > +[1, 15]
> > > > + * - For <src>, make sure <offset> bit backwards & <16 - offset> bit
> > > > +forwards are available for loading
> > > > + * - <dst>, <src>, <len> must be variables
> > > > + * - __m128i <xmm0> ~ <xmm8> must be pre-defined */ #define
> > > > +MOVEUNALIGNED_LEFT47_IMM(dst, src, len,
> > >
> > > Naive question:
> > > Is there a real benefit of using a macro compared to a static inline function
> > > optimized by a modern compiler?
> > >
> > The macro is in the existing DPDK codes. I didn't touch it. I just change the file name and the function name to rte_memcpy_internal.
> > So I am not clear about if there is real benefit.
> > In my opinion, I think it is the same as static inline function.
> > Do I need to change them to inline function?
> In this patch, it appears as a new macro.
Ah no, it definitely been there before.
All we did here - git mv rte_memcpy.h rte_memcpyu_interlan.h
and then in rte_memcpy_internal.h renamed rte_memcpy() to rte_memcpy_internal().
> If you can, inline function is cleaner for the new one.
I don't think it will be straightforward - one of the parameters is a constant value.
My preference would be to keep original rte_memcpy() code intact as much as we can here
(except probably cosmetic changes - indentation, line length fixing etc.).
After all that patch is for adding architecture function selection at runtime only.
If we like to improve our rte_memcpy() any furher - NP with that, but let it be a
> > > Anyway, if you are doing a new version, please reduce lines length and fix
> > > the indent from spaces to tabs.
> > >
> > They are original DPDK codes so I didn't touch them.
> > But in next version, I will fix them.
> Just to be sure: we are talking about fixing checkpatch warnings
> only for the code added, changed or moved.
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