On Wed, Jan 21, 2015 at 02:21:25PM +0100, Marc Sune wrote: > > On 21/01/15 14:02, Bruce Richardson wrote: > >On Wed, Jan 21, 2015 at 01:36:41PM +0100, Marc Sune wrote: > >>On 21/01/15 04:44, Wang, Zhihong wrote: > >>>>-----Original Message----- > >>>>From: Richardson, Bruce > >>>>Sent: Wednesday, January 21, 2015 12:15 AM > >>>>To: Neil Horman > >>>>Cc: Wang, Zhihong; dev at dpdk.org > >>>>Subject: Re: [dpdk-dev] [PATCH 0/4] DPDK memcpy optimization > >>>> > >>>>On Tue, Jan 20, 2015 at 10:11:18AM -0500, Neil Horman wrote: > >>>>>On Tue, Jan 20, 2015 at 03:01:44AM +0000, Wang, Zhihong wrote: > >>>>>>>-----Original Message----- > >>>>>>>From: Neil Horman [mailto:nhorman at tuxdriver.com] > >>>>>>>Sent: Monday, January 19, 2015 9:02 PM > >>>>>>>To: Wang, Zhihong > >>>>>>>Cc: dev at dpdk.org > >>>>>>>Subject: Re: [dpdk-dev] [PATCH 0/4] DPDK memcpy optimization > >>>>>>> > >>>>>>>On Mon, Jan 19, 2015 at 09:53:30AM +0800, zhihong.wang at 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. > >>>>>> > >>>>>ok, thank you. I'm all for optimzation, but I think a compile that > >>>>>takes almost > >>>>>10 minutes for a single file is going to generate some raised eyebrows > >>>>>when end users start tinkering with it > >>>>> > >>>>>Neil > >>>>> > >>>>>>Zhihong (John) > >>>>>> > >>>>Even two minutes is a very long time to compile, IMHO. The whole of DPDK > >>>>doesn't take that long to compile right now, and that's with a couple of > >>>>huge > >>>>header files with routing tables in it. Any chance you could cut compile > >>>>time > >>>>down to a few seconds while still having reasonable tests? > >>>>Also, when there is AVX2 present on the system, what is the compile time > >>>>like for that code? > >>>> > >>>> /Bruce > >>>Neil, Bruce, > >>> > >>>Some data first. > >>> > >>>Sandy Bridge without AVX2: > >>>1. original w/ 10 constant memcpy: 2'25" > >>>2. patch w/ 12 constant memcpy: 2'41" > >>>3. patch w/ 63 constant memcpy: 9'41" > >>> > >>>Haswell with AVX2: > >>>1. original w/ 10 constant memcpy: 1'57" > >>>2. patch w/ 12 constant memcpy: 1'56" > >>>3. patch w/ 63 constant memcpy: 3'16" > >>> > >>>Also, to address Bruce's question, we have to reduce test case to cut down > >>>compile time. Because we use: > >>>1. intrinsics instead of assembly for better flexibility and can utilize > >>>more compiler optimization > >>>2. complex function body for better performance > >>>3. inlining > >>>This increases compile time. > >>>But I think it'd be okay to do that as long as we can select a fair set of > >>>test points. > >>> > >>>It'd be great if you could give some suggestion, say, 12 points. > >>> > >>>Zhihong (John) > >>> > >>> > >>While I agree in the general case these long compilation times is painful > >>for the users, having a factor of 2-8x in memcpy operations is quite an > >>improvement, specially in DPDK applications which need to deal > >>(unfortunately) heavily on them -- e.g. IP fragmentation and reassembly. > >> > >>Why not having a fast compilation by default, and a tunable config flag to > >>enable a highly optimized version of rte_memcpy (e.g. RTE_EAL_OPT_MEMCPY)? > >> > >>Marc > >> > >Out of interest, are these 2-8x improvements something you have benchmarked > >in these app scenarios? [i.e. not just in micro-benchmarks]. > > How much that micro-speedup will end up affecting the performance of the > entire application is something I cannot say, so I agree that we should > probably have some additional benchmarks before deciding that pays off > maintaining 2 versions of rte_memcpy. > > There are however a bunch of possible DPDK applications that could > potentially benefit; IP fragmentation, tunneling and specialized DPI > applications, among others, since they involve a reasonable amount of > memcpys per pkt. My point was, *if* it proves that is enough beneficial, why > not having it optionally? > > Marc
I agree, if it provides the speedups then we need to have it in - and quite possibly on by default, even. /Bruce
