From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx.bisdn.de (mx.bisdn.de [185.27.182.31]) by dpdk.org (Postfix) with ESMTP id 821D65A15 for ; Wed, 21 Jan 2015 14:21:28 +0100 (CET) Received: from [172.16.250.156] (unknown [172.16.250.156]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mx.bisdn.de (Postfix) with ESMTPSA id CFE94A2FBF; Wed, 21 Jan 2015 14:21:27 +0100 (CET) Message-ID: <54BFA7D5.7020106@bisdn.de> Date: Wed, 21 Jan 2015 14:21:25 +0100 From: Marc Sune User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.3.0 MIME-Version: 1.0 To: Bruce Richardson References: <1421632414-10027-1-git-send-email-zhihong.wang@intel.com> <20150119130221.GB21790@hmsreliant.think-freely.org> <20150120151118.GD18449@hmsreliant.think-freely.org> <20150120161453.GA5316@bricha3-MOBL3> <54BF9D59.7070104@bisdn.de> <20150121130234.GB10756@bricha3-MOBL3> In-Reply-To: <20150121130234.GB10756@bricha3-MOBL3> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Cc: dev@dpdk.org Subject: Re: [dpdk-dev] [PATCH 0/4] DPDK memcpy optimization X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 21 Jan 2015 13:21:28 -0000 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@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@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. >>>>>> >>>>> 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 > > /Bruce