[dpdk-dev] [PATCH 1/4] eal/common: introduce rte_memset on IA platform

[Yao, Lei A]

> On Fri, Dec 16, 2016 at 10:19:43AM +0000, Yang, Zhiyong wrote:
> > > > I run the same virtio/vhost loopback tests without NIC.
> > > > I can see the  throughput drop  when running choosing functions at run
> > > > time compared to original code as following on the same platform(my
> > > machine is haswell)
> > > > 	Packet size	perf drop
> > > > 	64 		-4%
> > > > 	256 		-5.4%
> > > > 	1024		-5%
> > > > 	1500		-2.5%
> > > > Another thing, I run the memcpy_perf_autotest,  when N= <128, the
> > > > rte_memcpy perf gains almost disappears When choosing functions at
> run
> > > > time.  For N=other numbers, the perf gains will become narrow.
> > > >
> > > How narrow. How significant is the improvement that we gain from
> having to
> > > maintain our own copy of memcpy. If the libc version is nearly as good we
> > > should just use that.
> > >
> > > /Bruce
> >
> > Zhihong sent a patch about rte_memcpy,  From the patch,
> > we can see the optimization job for memcpy will bring obvious perf
> improvements
> > than glibc for DPDK.
> 
> Just a clarification: it's better than the __original DPDK__ rte_memcpy
> but not the glibc one. That makes me think have any one tested the memcpy
> with big packets? Does the one from DPDK outweigh the one from glibc,
> even for big packets?
> 
> 	--yliu
> 
I have test the loopback performanc rte_memcpy and glibc memcpy. For both small packer and
Big packet, rte_memcpy has better performance. My test enviromen is following
CPU: BDW
Ubutnu16.04
Kernal:  4.4.0
gcc : 5.4.0
Path: mergeable
Size       rte_memcpy performance gain
64           31%
128         35%
260         27%
520         33%
1024      18%
1500      12%

--Lei
> > http://www.dpdk.org/dev/patchwork/patch/17753/
> > git log as following:
> > This patch is tested on Ivy Bridge, Haswell and Skylake, it provides
> > up to 20% gain for Virtio Vhost PVP traffic, with packet size ranging
> > from 64 to 1500 bytes.
> >
> > thanks
> > Zhiyong