From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Horman Subject: Re: [PATCH v3 3/5] hash: add fallback to software CRC32 implementation Date: Tue, 18 Nov 2014 08:33:07 -0500 Message-ID: <20141118133307.GA32375@hmsreliant.think-freely.org> References: <1416160760-16087-1-git-send-email-e_zhumabekov@sts.kz> <546AD178.9070109@sts.kz> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Cc: dev-VfR2kkLFssw@public.gmane.org To: Yerden Zhumabekov Return-path: Content-Disposition: inline In-Reply-To: <546AD178.9070109-8EHiFRVJVgQ@public.gmane.org> List-Id: patches and discussions about DPDK List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces-VfR2kkLFssw@public.gmane.org Sender: "dev" On Tue, Nov 18, 2014 at 10:56:24AM +0600, Yerden Zhumabekov wrote: > Sorry, maybe I made a mistake here. >=20 > Accoring to lib/librte_eal/common/eal_common_cpuflags.c code, it seemed > to me that constructor attribute is not supported by intel compiler. So > in that case here I decided to leave the code for autodetection. Am I > correct? >=20 I don't think thats correct. The Intel Compiler claims support for most G= CC features, except where explicitly stated in the release notes, and I don'= t find any documentation clearly excepting the constructor attribute from that l= ist. That said, since the intel compiler isn't open, I don't have access to it= and cannot confirm either way, though if its the case, the DPDK has a major i= ssue, as __attribute__((constructor)) is used extensively throughout the code Neil > 18.11.2014 9:21, Yerden Zhumabekov =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > > 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. > > > > Depending on compiler attributes support, best available algorithm > > may be detected upon application startup. > > > > Signed-off-by: Yerden Zhumabekov > > --- > > lib/librte_hash/rte_hash_crc.h | 64 ++++++++++++++++++++++++++++++= ++++++++-- > > 1 file changed, 62 insertions(+), 2 deletions(-) > > > > diff --git a/lib/librte_hash/rte_hash_crc.h b/lib/librte_hash/rte_has= h_crc.h > > index 15f687a..c1b75e8 100644 > > --- a/lib/librte_hash/rte_hash_crc.h > > +++ b/lib/librte_hash/rte_hash_crc.h > > @@ -45,7 +45,11 @@ extern "C" { > > #endif > > =20 > > #include > > +#ifdef RTE_MACHINE_CPUFLAG_SSE4_2 > > #include > > +#endif > > +#include > > +#include > > =20 > > /* Lookup tables for software implementation of CRC32C */ > > static uint32_t crc32c_tables[8][256] =3D {{ > > @@ -363,8 +367,44 @@ crc32c_2words(uint64_t data, uint32_t init_val) > > return crc; > > } > > =20 > > +enum crc32_alg_t { > > + CRC32_SW =3D 0, > > + CRC32_SSE42, > > + CRC32_AUTODETECT > > +}; > > + > > +static enum crc32_alg_t crc32_alg =3D CRC32_AUTODETECT; > > + > > +/** > > + * 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 defa= ult > > + */ > > +static inline void > > +rte_hash_crc_set_alg(enum crc32_alg_t alg) > > +{ > > + int sse42_supp =3D rte_cpu_get_flag_enabled(RTE_CPUFLAG_SSE4_2); > > + enum crc32_alg_t alg_supp =3D sse42_supp ? CRC32_SSE42 : CRC32_SW; > > + crc32_alg =3D (alg =3D=3D CRC32_SSE42) ? alg_supp : CRC32_SW; > > +} > > + > > +/* Best available algorithm is detected via CPUID instruction */ > > +#ifndef __INTEL_COMPILER > > +static inline void __attribute__((constructor)) > > +rte_hash_crc_try_sse42(void) > > +{ > > + rte_hash_crc_set_alg(CRC32_SSE42); > > +} > > +#endif > > + > > /** > > * 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 +416,22 @@ 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 __INTEL_COMPILER > > + if (unlikely(crc32_alg =3D=3D CRC32_AUTODETECT)) > > + rte_hash_crc_set_alg(CRC32_SSE42); > > +#endif > > +#ifdef RTE_MACHINE_CPUFLAG_SSE4_2 > > + if (likely(crc32_alg =3D=3D CRC32_SSE42)) > > + return _mm_crc32_u32(init_val, data); > > +#endif > > + > > + return crc32c_1word(data, init_val); > > } > > =20 > > /** > > * Use single crc32 instruction to perform a hash on a 8 byte value. > > + * Fall back to software crc32 implementation in case SSE4.2 is > > + * not supported > > * > > * @param data > > * Data to perform hash on. > > @@ -392,7 +443,16 @@ rte_hash_crc_4byte(uint32_t data, uint32_t init_= val) > > static inline uint32_t > > rte_hash_crc_8byte(uint64_t data, uint32_t init_val) > > { > > - return _mm_crc32_u64(init_val, data); > > +#ifdef __INTEL_COMPILER > > + if (unlikely(crc32_alg =3D=3D CRC32_AUTODETECT)) > > + rte_hash_crc_set_alg(CRC32_SSE42); > > +#endif > > +#ifdef RTE_MACHINE_CPUFLAG_SSE4_2 > > + if (likely(crc32_alg =3D=3D CRC32_SSE42)) > > + return _mm_crc32_u64(init_val, data); > > +#endif > > + > > + return crc32c_2words(data, init_val); > > } > > =20 > > /** >=20 > --=20 > Sincerely, >=20 > Yerden Zhumabekov > State Technical Service > Astana, KZ >=20 >=20