> -----Original Message----- > From: Neil Horman [mailto:nhorman at tuxdriver.com] > Sent: Wednesday, January 21, 2015 8:38 PM > To: Ananyev, Konstantin > Cc: Wang, Zhihong; Richardson, Bruce; dev at dpdk.org > Subject: Re: [dpdk-dev] [PATCH 0/4] DPDK memcpy optimization > > On Wed, Jan 21, 2015 at 12:02:57PM +0000, Ananyev, Konstantin wrote: > > > > > > > -----Original Message----- > > > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Wang, Zhihong > > > Sent: Wednesday, January 21, 2015 3:44 AM > > > To: Richardson, Bruce; Neil Horman > > > Cc: dev at dpdk.org > > > Subject: Re: [dpdk-dev] [PATCH 0/4] DPDK memcpy optimization > > > > > > > > > > > > > -----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. > > > > We use instrincts and inlining in many other places too. > > Why it suddenly became a problem here? > I agree, something just doesnt feel right here. not sure what it is yet, but > I > don't see how a memcpy function can be so complex as to take almost 10 > minutes to compile. Its almost like we're recursively including something > here and its driving gcc into a huge loop Neil > > > Konstantin > > > > > 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) > > > > > > > > > > > > >
Konstantin, Bruce, Neil, The reason why it took so long is simply because there're too many function calls. Just keep in mind that there are (63 + 63) * 4 = 504 memcpy calls (inline) with constant length, gcc will unroll the memcpy function body and generate instructions directly for all of them based on the immediate value. I wrote a small program separately which contains the rte_memcpy.h and a "main" function that calls rte_memcpy 120 * 4 = 480 times with constant length, it took 11 minutes to compile. Also, the compile time doesn't grow linearly because 1 group (120) memcpy calls took less than 1 minute. So I think to reduce the compile time, we need to reduce the constant test case, like the original file in dpdk 1.8.0 has only (10 + 10)* 4 calls. To Konstantin, Intrinsics is not a problem, what I meant is that, if we write assembly, gcc may not have to optimize it, but if we use intrinsics, gcc will treat it like a piece of C code and do optimization, that may increase compile time. To Bruce, My previous compile time in this thread is measured like this: make clean ; rm -rf x86_64-native-linuxapp-gcc ; then make with j 1.