crypto: crc32c - Optimize CRC32C calculation with PCLMULQDQ instruction

This patch adds the crc_pcl function that calculates CRC32C checksum using the
PCLMULQDQ instruction on processors that support this feature. This will
provide speedup over using CRC32 instruction only.
The usage of PCLMULQDQ necessitate the invocation of kernel_fpu_begin and
kernel_fpu_end and incur some overhead.  So the new crc_pcl function is only
invoked for buffer size of 512 bytes or more.  Larger sized
buffers will expect to see greater speedup.  This feature is best used coupled
with eager_fpu which reduces the kernel_fpu_begin/end overhead.  For
buffer size of 1K the speedup is around 1.6x and for buffer size greater than
4K, the speedup is around 3x compared to original implementation in crc32c-intel
module. Test was performed on Sandy Bridge based platform with constant frequency
set for cpu.

A white paper detailing the algorithm can be found here:
http://download.intel.com/design/intarch/papers/323405.pdf

Signed-off-by: Tim Chen <tim.c.chen@linux.intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

1 files changed, 10 insertions, 0 deletions

diff --git a/crypto/Kconfig b/crypto/Kconfig
index 6563366bae80..b901b590635f 100644
--- a/crypto/Kconfig
+++ b/crypto/Kconfig
@@ -324,9 +324,19 @@ config CRYPTO_CRC32C
           by iSCSI for header and data digests and by others.
           See Castagnoli93.  Module will be crc32c.
 
+config CRYPTO_CRC32C_X86_64
+        bool
+        depends on X86 && 64BIT
+        select CRYPTO_HASH
+        help
+          In Intel processor with SSE4.2 supported, the processor will
+          support CRC32C calculation using hardware accelerated CRC32
+          instruction optimized with PCLMULQDQ instruction when available.
+
 config CRYPTO_CRC32C_INTEL
         tristate "CRC32c INTEL hardware acceleration"
         depends on X86
+        select CRYPTO_CRC32C_X86_64 if 64BIT
         select CRYPTO_HASH
         help
           In Intel processor with SSE4.2 supported, the processor will