From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from smtp.tuxdriver.com (charlotte.tuxdriver.com [70.61.120.58]) by dpdk.org (Postfix) with ESMTP id 37DD15323 for ; Tue, 18 Nov 2014 16:49:50 +0100 (CET) Received: from hmsreliant.think-freely.org ([2001:470:8:a08:7aac:c0ff:fec2:933b] helo=localhost) by smtp.tuxdriver.com with esmtpsa (TLSv1:AES128-SHA:128) (Exim 4.63) (envelope-from ) id 1XqlCH-00032k-Vr; Tue, 18 Nov 2014 11:00:08 -0500 Date: Tue, 18 Nov 2014 11:00:05 -0500 From: Neil Horman To: Yerden Zhumabekov Message-ID: <20141118160005.GC32375@hmsreliant.think-freely.org> References: <1409724351-23786-1-git-send-email-e_zhumabekov@sts.kz> <20141118144138.GB32375@hmsreliant.think-freely.org> <546B607B.9030808@sts.kz> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <546B607B.9030808@sts.kz> User-Agent: Mutt/1.5.23 (2014-03-12) X-Spam-Score: -2.9 (--) X-Spam-Status: No Cc: "dev@dpdk.org" Subject: Re: [dpdk-dev] [PATCH v4 3/5] hash: add fallback to software CRC32 implementation 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: Tue, 18 Nov 2014 15:49:50 -0000 On Tue, Nov 18, 2014 at 09:06:35PM +0600, Yerden Zhumabekov wrote: > > 18.11.2014 20:41, Neil Horman пишет: > > On Tue, Nov 18, 2014 at 08:03:40PM +0600, Yerden Zhumabekov wrote: > >> Initially, SSE4.2 support is detected via CPUID instruction. > >> > >> Added rte_hash_crc_set_alg() function to detect and set CRC32 > >> implementation if necessary. SSE4.2 is allowed by default. If it's > >> not available, fall back to sw implementation. > >> > >> Best available algorithm is detected upon application startup > >> through the constructor function rte_hash_crc_try_sse442(). > >> > >> Signed-off-by: Yerden Zhumabekov > >> --- > >> lib/librte_hash/rte_hash_crc.h | 53 ++++++++++++++++++++++++++++++++++++++-- > >> 1 file changed, 51 insertions(+), 2 deletions(-) > >> > >> diff --git a/lib/librte_hash/rte_hash_crc.h b/lib/librte_hash/rte_hash_crc.h > >> index 15f687a..332ed99 100644 > >> --- a/lib/librte_hash/rte_hash_crc.h > >> +++ b/lib/librte_hash/rte_hash_crc.h > >> @@ -45,7 +45,11 @@ extern "C" { > >> #endif > >> > >> #include > >> +#ifdef RTE_MACHINE_CPUFLAG_SSE4_2 > >> #include > >> +#endif > >> +#include > >> +#include > >> > >> /* Lookup tables for software implementation of CRC32C */ > >> static uint32_t crc32c_tables[8][256] = {{ > >> @@ -363,8 +367,41 @@ crc32c_2words(uint64_t data, uint32_t init_val) > >> return crc; > >> } > >> > >> +enum crc32_alg_t { > >> + CRC32_SW = 0, > >> + CRC32_SSE42 > >> +}; > >> + > >> +static enum crc32_alg_t crc32_alg; > >> + > >> +/** > >> + * Allow or disallow use of SSE4.2 instrinsics for CRC32 hash > >> + * calculation. > >> + * > >> + * @param flag > >> + * unsigned integer flag > >> + * - (CRC32_SW) Don't use SSE4.2 intrinsics > >> + * - (CRC32_SSE42) Use SSE4.2 intrinsics if available, set by default > >> + */ > >> +static inline void > >> +rte_hash_crc_set_alg(enum crc32_alg_t alg) > >> +{ > >> + int sse42_supp = rte_cpu_get_flag_enabled(RTE_CPUFLAG_SSE4_2); > >> + enum crc32_alg_t alg_supp = sse42_supp ? CRC32_SSE42 : CRC32_SW; > >> + crc32_alg = (alg == CRC32_SSE42) ? alg_supp : CRC32_SW; > >> +} > >> + > >> +/* Best available algorithm is detected via CPUID instruction */ > >> +static inline void __attribute__((constructor)) > >> +rte_hash_crc_try_sse42(void) > >> +{ > >> + rte_hash_crc_set_alg(CRC32_SSE42); > >> +} > >> + > >> /** > >> * Use single crc32 instruction to perform a hash on a 4 byte value. > >> + * Fall back to software crc32 implementation in case SSE4.2 is > >> + * not supported > >> * > >> * @param data > >> * Data to perform hash on. > >> @@ -376,11 +413,18 @@ crc32c_2words(uint64_t data, uint32_t init_val) > >> static inline uint32_t > >> rte_hash_crc_4byte(uint32_t data, uint32_t init_val) > >> { > >> - return _mm_crc32_u32(init_val, data); > >> +#ifdef RTE_MACHINE_CPUFLAG_SSE4_2 > >> + if (likely(crc32_alg == CRC32_SSE42)) > >> + return _mm_crc32_u32(init_val, data); > >> +#endif > > you don't really need these ifdefs here anymore given that you have a > > constructor to do the algorithm selection. In fact you need to remove them, in > > the event you build on a system that doesn't support SSE42, but run on a system > > that does. > > Originally, I thought so as well. I wrote the code without these ifdefs, > but it didn't compile on my machine which doesn't support SSE4.2. Error > was triggered by nmmintrin.h which has a check for respective GCC > extension. So I think these ifdefs are indeed required. > You need to edit the makefile so that the compiler gets passed the option -msse42. That way it will know to emit sse42 instructions. It will also allow you to remove the ifdef from the include file Neil > -- > Sincerely, > > Yerden Zhumabekov > State Technical Service > Astana, KZ > > >