Messages in this thread | | | Subject | Re: [PATCH] Performance Improvement in CRC16 Calculations. | From | Christophe LEROY <> | Date | Thu, 16 Aug 2018 17:41:13 +0200 |
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Hi,
Please include your new patch as plain text inside the mail, not as a MIME attachment. Otherwise it is not downloadable from https://patchwork.kernel.org/patch/10563093/
Christophe
Le 16/08/2018 à 16:22, Douglas Gilbert a écrit : > Hi, > Rather than present this formerly as an alternate patch, attached is a > clean-up of my patch which uses the variable size table proposed by > Joe Perches <joe@perches.com> and is based on the original patch that > started this thread. > > Doug Gilbert > > On 2018-08-16 10:02 AM, Jeffrey Lien wrote: >> Eric, >> We did not test the slice by 4 or 8 tables. I'm not sure of the >> value of doing that since the slice by 16 will provide the best >> performance gain. If I'm missing anything here, please let me know. >> >> I'm working on a new version of the patch based on the feedback from >> others and will also change the pointer variables to start with p and >> fix the indenting you mentioned below in the new version of the patch. >> >> Thanks >> >> Jeff Lien >> >> -----Original Message----- >> From: Eric Biggers [mailto:ebiggers@kernel.org] >> Sent: Friday, August 10, 2018 3:16 PM >> To: Jeffrey Lien <Jeff.Lien@wdc.com> >> Cc: 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 >> <david.darrington@wdc.com>; Jeff Furlong <jeff.furlong@wdc.com> >> Subject: Re: [PATCH] Performance Improvement in CRC16 Calculations. >> >> On Fri, Aug 10, 2018 at 02:12:11PM -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. >>> >>> FIO Sequential Write, 64K Block Size, Queue Depth 64 >>> BE Base Kernel: bw=201.5 MiB/s >>> BE Modified CRC Calc: bw=968.1 MiB/s >>> 4.80x performance improvement >>> >>> LE Base Kernel: bw=357 MiB/s >>> LE Modified CRC Calc: bw=1964 MiB/s >>> 5.51x performance improvement >>> >>> FIO Sequential Read, 64K Block Size, Queue Depth 64 >>> BE Base Kernel: bw=611.2 MiB/s >>> BE Modified CRC calc: bw=684.9 MiB/s >>> 1.12x performance improvement >>> >>> LE Base Kernel: bw=797 MiB/s >>> LE Modified CRC Calc: bw=2730 MiB/s >>> 3.42x performance improvement >> >> Did you also test the slice-by-4 (requires 2048-byte table) and >> slice-by-8 (requires 4096-byte table) methods? Your proposal is >> slice-by-16 (requires 8192-byte table); the original was slice-by-1 >> (requires 512-byte table). >> >>> __u16 crc_t10dif_generic(__u16 crc, const unsigned char *buffer, >>> size_t len) { >>> - unsigned int i; >>> + const __u8 *i = (const __u8 *)buffer; >>> + const __u8 *i_end = i + len; >>> + const __u8 *i_last16 = i + (len / 16 * 16); >> >> 'i' is normally a loop counter, not a pointer. >> Use 'p', 'p_end', and 'p_last16'. >> >>> - for (i = 0 ; i < len ; i++) >>> - crc = (crc << 8) ^ t10_dif_crc_table[((crc >> 8) ^ >>> buffer[i]) & 0xff]; >>> + for (; i < i_last16; i += 16) { >>> + crc = t10_dif_crc_table[15][i[0] ^ (__u8)(crc >> 8)] ^ >>> + t10_dif_crc_table[14][i[1] ^ (__u8)(crc >> 0)] ^ >>> + t10_dif_crc_table[13][i[2]] ^ >>> + t10_dif_crc_table[12][i[3]] ^ >>> + t10_dif_crc_table[11][i[4]] ^ >>> + t10_dif_crc_table[10][i[5]] ^ >>> + t10_dif_crc_table[9][i[6]] ^ >>> + t10_dif_crc_table[8][i[7]] ^ >>> + t10_dif_crc_table[7][i[8]] ^ >>> + t10_dif_crc_table[6][i[9]] ^ >>> + t10_dif_crc_table[5][i[10]] ^ >>> + t10_dif_crc_table[4][i[11]] ^ >>> + t10_dif_crc_table[3][i[12]] ^ >>> + t10_dif_crc_table[2][i[13]] ^ >>> + t10_dif_crc_table[1][i[14]] ^ >>> + t10_dif_crc_table[0][i[15]]; >>> + } >> >> Please indent this properly. >> >> crc = t10_dif_crc_table[15][i[0] ^ (__u8)(crc >> 8)] ^ >> t10_dif_crc_table[14][i[1] ^ (__u8)(crc >> 0)] ^ >> t10_dif_crc_table[13][i[2]] ^ >> t10_dif_crc_table[12][i[3]] ^ >> t10_dif_crc_table[11][i[4]] ^ >> ... >> >> - Eric >> >
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