From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neil Horman Subject: Re: [PATCH v4 3/5] hash: add fallback to software CRC32 implementation Date: Tue, 18 Nov 2014 12:46:19 -0500 Message-ID: <20141118174619.GE32375@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> <20141118160005.GC32375@hmsreliant.think-freely.org> <546B7E2D.7050705@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: <546B7E2D.7050705-8EHiFRVJVgQ@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 11:13:17PM +0600, Yerden Zhumabekov wrote: >=20 > 18.11.2014 22:00, Neil Horman =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > > On Tue, Nov 18, 2014 at 09:06:35PM +0600, Yerden Zhumabekov wrote: > >> 18.11.2014 20:41, Neil Horman =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > >>> On Tue, Nov 18, 2014 at 08:03:40PM +0600, Yerden Zhumabekov wrote: > >>>> /** > >>>> * Use single crc32 instruction to perform a hash on a 4 byte val= ue. > >>>> + * 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_v= al) > >>>> 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 =3D=3D 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 rem= ove 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 ifd= efs, > >> but it didn't compile on my machine which doesn't support SSE4.2. Er= ror > >> 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 op= tion > > -msse42. That way it will know to emit sse42 instructions. It will a= lso allow > > you to remove the ifdef from the include file >=20 > In this case, I guess there are two options: > 1) modify all makefiles which use librte_hash > 2) move all function bodies from rte_hash_crc.h to separate module, > leaving prototype definitions there only. >=20 > Everybody's up for the second option? :) >=20 Crud, you're right, I didn't think about the header inclusion issue. Is = it worth adding the jump to enable the dynamic hash selection? Neil > --=20 > Sincerely, >=20 > Yerden Zhumabekov > State Technical Service > Astana, KZ >=20 >=20 >=20