Re: [PATCH] Performance Improvement in CRC16 Calculations.

On Fri, 2018-08-10 at 16:02 -0400, Nicolas Pitre wrote:

quoted

On Fri, 10 Aug 2018, Joe Perches wrote:

quoted

On Fri, 2018-08-10 at 14:12 -0500, Jeff Lien wrote:

quoted

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