From: Douglas Gilbert Subject: Re: [PATCH] Performance Improvement in CRC16 Calculations. Date: Fri, 10 Aug 2018 22:39:19 -0400 Message-ID: <75d66dfa-688b-f941-04fd-5a39cf882b21@interlog.com> References: <1533928331-21303-1-git-send-email-jeff.lien@wdc.com> <9b5b906f42dfab78f382c90f66851717d258a15d.camel@perches.com> Reply-To: dgilbert@interlog.com Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Cc: Jeff Lien , linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org, linux-block@vger.kernel.org, linux-scsi@vger.kernel.org, herbert@gondor.apana.org.au, tim.c.chen@linux.intel.com, martin.petersen@oracle.com, david.darrington@wdc.com, jeff.furlong@wdc.com To: Joe Perches , Nicolas Pitre Return-path: In-Reply-To: Content-Language: en-CA Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org On 2018-08-10 08:11 PM, Joe Perches wrote: > On Fri, 2018-08-10 at 16:02 -0400, Nicolas Pitre wrote: >> On Fri, 10 Aug 2018, Joe Perches wrote: >> >>> On Fri, 2018-08-10 at 14:12 -0500, Jeff Lien wrote: >>>> This patch provides a performance improvement for the CRC16 calculations done in read/write >>>> workloads using the T10 Type 1/2/3 guard field. For example, today with sequential write >>>> workloads (one thread/CPU of IO) we consume 100% of the CPU because of the CRC16 computation >>>> bottleneck. Today's block devices are considerably faster, but the CRC16 calculation prevents >>>> folks from utilizing the throughput of such devices. To speed up this calculation and expose >>>> the block device throughput, we slice the old single byte for loop into a 16 byte for loop, >>>> with a larger CRC table to match. The result has shown 5x performance improvements on various >>>> big endian and little endian systems running the 4.18.0 kernel version. >>> >>> Thanks. >>> >>> This seems a sensible tradeoff for the 4k text size increase. >> >> More like 7.5KB. Would be best if this was configurable so the small >> version remained available. > > Maybe something like: (compiled, untested) > --- > crypto/Kconfig | 10 + > crypto/crct10dif_common.c | 543 +++++++++++++++++++++++++++++++++++++++++++++- > 2 files changed, 549 insertions(+), 4 deletions(-) > > diff --git a/crypto/Kconfig b/crypto/Kconfig > index f3e40ac56d93..88d9d17bb18a 100644 > --- a/crypto/Kconfig > +++ b/crypto/Kconfig > @@ -618,6 +618,16 @@ config CRYPTO_CRCT10DIF > a crypto transform. This allows for faster crc t10 diff > transforms to be used if they are available. > > +config CRYPTO_CRCT10DIF_TABLE_SIZE > + int "Size of CRCT10DIF crc tables (as a power of 2)" > + depends on CRYPTO_CRCT10DIF > + range 1 5 > + default 1 if EMBEDDED > + default 5 > + help > + Set the table size used by the CRYPTO_CRCT10DIF crc calculation > + Larger values use more memory and are faster. > + > config CRYPTO_CRCT10DIF_PCLMUL > tristate "CRCT10DIF PCLMULQDQ hardware acceleration" > depends on X86 && 64BIT && CRC_T10DIF > diff --git a/crypto/crct10dif_common.c b/crypto/crct10dif_common.c > index b2fab366f518..4eb1c50c3688 100644 > --- a/crypto/crct10dif_common.c > +++ b/crypto/crct10dif_common.c > @@ -32,7 +32,8 @@ > * x^16 + x^15 + x^11 + x^9 + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1 > * gt: 0x8bb7 > */ > -static const __u16 t10_dif_crc_table[256] = { > +static const __u16 t10dif_crc_table[][256] = { > + { > + }, > +#endif > }; > > __u16 crc_t10dif_generic(__u16 crc, const unsigned char *buffer, size_t len) > { > - unsigned int i; > + const u8 *ptr = (const __u8 *)buffer; > + const u8 *ptr_end = ptr + len; > +#if CONFIG_CRYPTO_CRCT10DIF_TABLE_SIZE > 1 > + size_t tablesize = 1 << (CONFIG_CRYPTO_CRCT10DIF_TABLE_SIZE - 1); > + const u8 *ptr_last = ptr + (len / tablesize * tablesize); > > - for (i = 0 ; i < len ; i++) > - crc = (crc << 8) ^ t10_dif_crc_table[((crc >> 8) ^ buffer[i]) & 0xff]; > + while (ptr < ptr_last) { > + size_t index = tablesize; > + __u16 t; > + > + t = t10dif_crc_table[--index][*ptr++ ^ (u8)(crc >> 8)]; > + t ^= t10dif_crc_table[--index][*ptr++ ^ (u8)crc]; > + crc = t; > + while (index > 0) > + crc ^= t10dif_crc_table[--index][*ptr++]; > + } > +#endif > + while (ptr < ptr_end) > + crc = t10dif_crc_table[0][*ptr++ ^ (u8)(crc >> 8)] ^ (crc << 8); > > return crc; > } > > It is a bit messy but below is a copy and paste of a table 27 from draft SBC-4 revision 15 in chapter 4.22.4.4 on page 87. Table 27 — CRC test cases Pattern 32 bytes each set to 00h CRC=0000h 32 bytes each set to FFh CRC=A293h 32 bytes of an incrementing pattern from 00h to 1Fh CRC=0224h 2 bytes each set to FFh followed by 30 bytes set to 00h CRC=21B8h 32 bytes of a decrementing pattern from FFh to E0h CRC=A0B7h There is also example C code for its calculation in Annex C on pages 375 and 376. Doug Gilbert