Re: [dpdk-dev] [PATCH 0/4] DPDK memcpy optimization

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

> -----Original Message-----
> From: Neil Horman [mailto:nhorman@tuxdriver.com]
> Sent: Monday, January 19, 2015 9:02 PM
> To: Wang, Zhihong
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH 0/4] DPDK memcpy optimization
> 
> On Mon, Jan 19, 2015 at 09:53:30AM +0800, zhihong.wang@intel.com wrote:
> > This patch set optimizes memcpy for DPDK for both SSE and AVX platforms.
> > It also extends memcpy test coverage with unaligned cases and more test
> points.
> >
> > Optimization techniques are summarized below:
> >
> > 1. Utilize full cache bandwidth
> >
> > 2. Enforce aligned stores
> >
> > 3. Apply load address alignment based on architecture features
> >
> > 4. Make load/store address available as early as possible
> >
> > 5. General optimization techniques like inlining, branch reducing,
> > prefetch pattern access
> >
> > Zhihong Wang (4):
> >   Disabled VTA for memcpy test in app/test/Makefile
> >   Removed unnecessary test cases in test_memcpy.c
> >   Extended test coverage in test_memcpy_perf.c
> >   Optimized memcpy in arch/x86/rte_memcpy.h for both SSE and AVX
> >     platforms
> >
> >  app/test/Makefile                                  |   6 +
> >  app/test/test_memcpy.c                             |  52 +-
> >  app/test/test_memcpy_perf.c                        | 238 +++++---
> >  .../common/include/arch/x86/rte_memcpy.h           | 664
> +++++++++++++++------
> >  4 files changed, 656 insertions(+), 304 deletions(-)
> >
> > --
> > 1.9.3
> >
> >
> Are you able to compile this with gcc 4.9.2?  The compilation of
> test_memcpy_perf is taking forever for me.  It appears hung.
> Neil


Neil,

Thanks for reporting this!
It should compile but will take quite some time if the CPU doesn't support AVX2, the reason is that:
1. The SSE & AVX memcpy implementation is more complicated than AVX2 version thus the compiler takes more time to compile and optimize
2. The new test_memcpy_perf.c contains 126 constants memcpy calls for better test case coverage, that's quite a lot

I've just tested this patch on an Ivy Bridge machine with GCC 4.9.2:
1. The whole compile process takes 9'41" with the original test_memcpy_perf.c (63 + 63 = 126 constant memcpy calls)
2. It takes only 2'41" after I reduce the constant memcpy call number to 12 + 12 = 24

I'll reduce memcpy call in the next version of patch.

Zhihong (John)