> -----Original Message----- > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Bruce Richardson > Sent: Wednesday, January 21, 2015 9:26 PM > To: Marc Sune > Cc: dev at dpdk.org > Subject: Re: [dpdk-dev] [PATCH 0/4] DPDK memcpy optimization > > 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
Since we're clear now that the long compile time is mainly caused by too many inline function calls, I think it's okay not to do this. Would you agree? Zhihong (John)
