ICP: Improve AES-GCM performance

Currently SIMD accelerated AES-GCM performance is limited by two
factors:

a. The need to disable preemption and interrupts and save the FPU
state before using it and to do the reverse when done. Due to the
way the code is organized (see (b) below) we have to pay this price
twice for each 16 byte GCM block processed.

b. Most processing is done in C, operating on single GCM blocks.
The use of SIMD instructions is limited to the AES encryption of the
counter block (AES-NI) and the Galois multiplication (PCLMULQDQ).
This leads to the FPU not being fully utilized for crypto
operations.

To solve (a) we do crypto processing in larger chunks while owning
the FPU. An `icp_gcm_avx_chunk_size` module parameter was introduced
to make this chunk size tweakable. It defaults to 32 KiB. This step
alone roughly doubles performance. (b) is tackled by porting and
using the highly optimized openssl AES-GCM assembler routines, which
do all the processing (CTR, AES, GMULT) in a single routine. Both
steps together result in up to 32x reduction of the time spend in
the en/decryption routines, leading up to approximately 12x
throughput increase for large (128 KiB) blocks.

Lastly, this commit changes the default encryption algorithm from
AES-CCM to AES-GCM when setting the `encryption=on` property.

Reviewed-By: Brian Behlendorf <[email protected]>
Reviewed-By: Jason King <[email protected]>
Reviewed-By: Tom Caputi <[email protected]>
Reviewed-By: Richard Laager <[email protected]>
Signed-off-by: Attila Fülöp <[email protected]>
Closes #9749 

1 files changed, 1 insertions, 1 deletions

diff --git a/include/sys/zio.h b/include/sys/zio.h
index 46f90a062..f78b02fd5 100644
--- a/include/sys/zio.h
+++ b/include/sys/zio.h
@@ -119,7 +119,7 @@ enum zio_encrypt {
 	ZIO_CRYPT_FUNCTIONS
 };
 
-#define	ZIO_CRYPT_ON_VALUE	ZIO_CRYPT_AES_256_CCM
+#define	ZIO_CRYPT_ON_VALUE	ZIO_CRYPT_AES_256_GCM
 #define	ZIO_CRYPT_DEFAULT	ZIO_CRYPT_OFF
 
 /* macros defining encryption lengths */