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From: Bruce Richardson <bruce.richardson@intel.com>
To: Neil Horman <nhorman@tuxdriver.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v4 3/5] hash: add fallback to software CRC32 implementation
Date: Tue, 18 Nov 2014 16:04:26 +0000	[thread overview]
Message-ID: <20141118160425.GA5840@bricha3-MOBL3> (raw)
In-Reply-To: <20141118160005.GC32375@hmsreliant.think-freely.org>

On Tue, Nov 18, 2014 at 11:00:05AM -0500, Neil Horman wrote:
> 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 <e_zhumabekov@sts.kz>
> > >> ---
> > >>  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 <stdint.h>
> > >> +#ifdef RTE_MACHINE_CPUFLAG_SSE4_2
> > >>  #include <nmmintrin.h>
> > >> +#endif
> > >> +#include <rte_cpuflags.h>
> > >> +#include <rte_branch_prediction.h>
> > >>  
> > >>  /* 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
> 

Question: does that then limit the compiler to emitting sse42 instructions? If,
for instance, the rest of DPDK is being compiled for a target supporting AVX2,
does that flag then prevent the compiler from auto-vectorising using SSE?

/Bruce

  reply	other threads:[~2014-11-18 15:55 UTC|newest]

Thread overview: 98+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-09-03  6:05 [dpdk-dev] [PATCH 0/2] rewritten rte_hash_crc() call Yerden Zhumabekov
2014-09-03  6:05 ` [dpdk-dev] [PATCH 1/2] hash: add new rte_hash_crc_8byte call Yerden Zhumabekov
2014-09-03  6:05 ` [dpdk-dev] [PATCH 2/2] hash: rte_hash_crc uses 8- and 4-byte CRC32 intrinsics Yerden Zhumabekov
2014-11-13 17:33 ` [dpdk-dev] [PATCH 0/2] rewritten rte_hash_crc() call Thomas Monjalon
2014-11-14  0:52   ` Neil Horman
2014-11-14  7:15     ` Yerden Zhumabekov
2014-11-14 11:33       ` Neil Horman
2014-11-14 11:57         ` Yerden Zhumabekov
2014-11-14 13:53           ` Neil Horman
2014-11-14 14:33             ` Thomas Monjalon
2014-11-14 16:43             ` Yerden Zhumabekov
2014-11-14 18:41               ` Neil Horman
2014-11-15 21:45                 ` Yerden Zhumabekov
2014-11-16 17:59 ` [dpdk-dev] [PATCH v2 0/4] rte_hash_crc reworked to be platform-independent Yerden Zhumabekov
2014-11-17 11:31   ` Neil Horman
2014-11-17 11:54     ` Yerden Zhumabekov
2014-11-25 17:05       ` Stephen Hemminger
2014-11-18  3:21   ` [dpdk-dev] [PATCH v3 0/5] " Yerden Zhumabekov
2014-11-18  3:21     ` [dpdk-dev] [PATCH v3 1/5] hash: add software CRC32 implementation Yerden Zhumabekov
2014-11-25 17:34       ` Stephen Hemminger
2014-11-18  3:21     ` [dpdk-dev] [PATCH v3 2/5] hash: add new rte_hash_crc_8byte call Yerden Zhumabekov
2014-11-18  3:21     ` [dpdk-dev] [PATCH v3 3/5] hash: add fallback to software CRC32 implementation Yerden Zhumabekov
2014-11-18  4:56       ` Yerden Zhumabekov
2014-11-18 13:33         ` Neil Horman
2014-11-18 13:37           ` Yerden Zhumabekov
2014-11-18 13:43           ` Thomas Monjalon
2014-11-18  3:21     ` [dpdk-dev] [PATCH v3 4/5] hash: rte_hash_crc() slices data into 8-byte pieces Yerden Zhumabekov
2014-11-18  3:25     ` [dpdk-dev] [PATCH v3 5/5] test: remove redundant compile checks Yerden Zhumabekov
2014-11-16 17:59 ` [dpdk-dev] [PATCH v2 1/4] hash: add software CRC32 implementation Yerden Zhumabekov
2014-11-16 17:59 ` [dpdk-dev] [PATCH v2 2/4] hash: add new rte_hash_crc_8byte call Yerden Zhumabekov
2014-11-16 17:59 ` [dpdk-dev] [PATCH v2 3/4] hash: add fallback to software CRC32 implementation Yerden Zhumabekov
2014-11-17 12:34   ` Ananyev, Konstantin
2014-11-17 12:41     ` Yerden Zhumabekov
2014-11-17 14:06     ` Neil Horman
2014-11-16 17:59 ` [dpdk-dev] [PATCH v2 4/4] hash: rte_hash_crc() slices data into 8-byte pieces Yerden Zhumabekov
2014-11-18 14:03 ` [dpdk-dev] [PATCH v4 0/5] rte_hash_crc reworked to be platform-independent Yerden Zhumabekov
2014-11-18 14:03   ` [dpdk-dev] [PATCH v4 1/5] hash: add software CRC32 implementation Yerden Zhumabekov
2014-11-18 14:03   ` [dpdk-dev] [PATCH v4 2/5] hash: add new rte_hash_crc_8byte call Yerden Zhumabekov
2014-11-18 14:03   ` [dpdk-dev] [PATCH v4 3/5] hash: add fallback to software CRC32 implementation Yerden Zhumabekov
2014-11-18 14:41     ` Neil Horman
2014-11-18 15:06       ` Yerden Zhumabekov
2014-11-18 16:00         ` Neil Horman
2014-11-18 16:04           ` Bruce Richardson [this message]
2014-11-18 16:08             ` Bruce Richardson
2014-11-18 16:38             ` Neil Horman
2014-11-18 17:13           ` Yerden Zhumabekov
2014-11-18 17:29             ` Wang, Shawn
2014-11-19  4:07               ` Yerden Zhumabekov
2014-11-18 17:46             ` Neil Horman
2014-11-18 17:52               ` Bruce Richardson
2014-11-18 21:36                 ` Neil Horman
2014-11-19  3:51                   ` Yerden Zhumabekov
2014-11-19 10:16                   ` Bruce Richardson
2014-11-19 11:34                     ` Neil Horman
2014-11-19 11:38                       ` Bruce Richardson
2014-11-19 11:50                         ` Ananyev, Konstantin
2014-11-19 11:59                           ` Yerden Zhumabekov
2014-11-19 15:05                           ` Neil Horman
2014-11-19 16:51                             ` Ananyev, Konstantin
2014-11-19 11:35                     ` Yerden Zhumabekov
2014-11-19 15:07                       ` Neil Horman
2014-11-20  3:04                         ` Yerden Zhumabekov
2014-11-18 17:58               ` Yerden Zhumabekov
2014-11-18 14:03   ` [dpdk-dev] [PATCH v4 4/5] hash: rte_hash_crc() slices data into 8-byte pieces Yerden Zhumabekov
2014-11-18 14:05   ` [dpdk-dev] [PATCH v4 5/5] test: remove redundant compile checks Yerden Zhumabekov
2014-11-20  5:15 ` [dpdk-dev] [PATCH v5 0/7] rte_hash_crc reworked to be platform-independent Yerden Zhumabekov
2014-11-20  5:16   ` [dpdk-dev] [PATCH v5 1/7] hash: add software CRC32 implementation Yerden Zhumabekov
2014-11-20  5:16   ` [dpdk-dev] [PATCH v5 2/7] hash: add assembly implementation of CRC32 intrinsics Yerden Zhumabekov
2014-11-20  5:16   ` [dpdk-dev] [PATCH v5 3/7] hash: replace built-in functions implementing SSE4.2 Yerden Zhumabekov
2014-11-20  5:16   ` [dpdk-dev] [PATCH v5 4/7] hash: add rte_hash_crc_8byte function Yerden Zhumabekov
2014-11-21 11:22     ` Neil Horman
2014-11-21 11:26       ` Yerden Zhumabekov
2014-11-20  5:17   ` [dpdk-dev] [PATCH v5 6/7] hash: rte_hash_crc() slices data into 8-byte pieces Yerden Zhumabekov
2014-11-20  5:17   ` [dpdk-dev] [PATCH v5 7/7] test: remove redundant compile checks Yerden Zhumabekov
2014-11-20  5:17   ` [dpdk-dev] [PATCH v5 5/7] hash: add fallback to software CRC32 implementation Yerden Zhumabekov
2014-11-27 21:04   ` [dpdk-dev] [PATCH v5 0/7] rte_hash_crc reworked to be platform-independent Thomas Monjalon
2014-11-28  3:28     ` Yerden Zhumabekov
2015-01-29  8:48 ` [dpdk-dev] [PATCH v6 " Yerden Zhumabekov
2015-01-29  8:48   ` [dpdk-dev] [PATCH v6 1/7] hash: add software CRC32 implementation Yerden Zhumabekov
2015-01-29  8:48   ` [dpdk-dev] [PATCH v6 2/7] hash: add assembly implementation of CRC32 intrinsics Yerden Zhumabekov
2015-02-02  5:15     ` Liang, Cunming
2015-02-02  5:34       ` Yerden Zhumabekov
2015-02-02  5:59         ` Liang, Cunming
2015-01-29  8:49   ` [dpdk-dev] [PATCH v6 3/7] hash: replace built-in functions implementing SSE4.2 Yerden Zhumabekov
2015-01-29  8:49   ` [dpdk-dev] [PATCH v6 4/7] hash: add rte_hash_crc_8byte function Yerden Zhumabekov
2015-01-29  8:50   ` [dpdk-dev] [PATCH v6 5/7] hash: add fallback to software CRC32 implementation Yerden Zhumabekov
2015-01-29  8:50   ` [dpdk-dev] [PATCH v6 6/7] hash: rte_hash_crc() slices data into 8-byte pieces Yerden Zhumabekov
2015-01-29  8:50   ` [dpdk-dev] [PATCH v6 7/7] test: remove redundant compile checks Yerden Zhumabekov
2015-02-01 14:13   ` [dpdk-dev] [PATCH v6 0/7] rte_hash_crc reworked to be platform-independent Neil Horman
2015-02-02  3:07     ` Yerden Zhumabekov
2015-02-02  3:31       ` Neil Horman
2015-02-02  5:18         ` [dpdk-dev] HA: " Жумабеков Ерден Мирзагулович
2015-02-02  5:39         ` [dpdk-dev] " Yerden Zhumabekov
2015-02-19 15:21           ` Bruce Richardson
2015-02-23 17:36             ` Thomas Monjalon
2015-02-24  3:00               ` Yerden Zhumabekov
2015-02-24  3:10                 ` Thomas Monjalon
2015-02-24  9:12                   ` Bruce Richardson

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