Implementation of AVX2 optimized Fletcher-4

New functionality:
- Preserves existing scalar implementation.
- Adds AVX2 optimized Fletcher-4 computation.
- Fastest routines selected on module load (benchmark).
- Test case for Fletcher-4 added to ztest.

New zcommon module parameters:
-  zfs_fletcher_4_impl (str): selects the implementation to use.
    "fastest" - use the fastest version available
    "cycle"   - cycle trough all available impl for ztest
    "scalar"  - use the original version
    "avx2"    - new AVX2 implementation if available

Performance comparison (Intel i7 CPU, 1MB data buffers):
- Scalar:  4216 MB/s
- AVX2:   14499 MB/s

See contents of `/sys/module/zcommon/parameters/zfs_fletcher_4_impl`
to get list of supported values. If an implementation is not supported
on the system, it will not be shown. Currently selected option is
enclosed in `[]`.

Signed-off-by: Jinshan Xiong <[email protected]>
Signed-off-by: Andreas Dilger <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #4330

1 files changed, 3 insertions, 0 deletions

diff --git a/module/zcommon/zfs_prop.c b/module/zcommon/zfs_prop.c
index 5a88cbe6c..76d564b43 100644
--- a/module/zcommon/zfs_prop.c
+++ b/module/zcommon/zfs_prop.c
@@ -35,6 +35,7 @@
 
 #include "zfs_prop.h"
 #include "zfs_deleg.h"
+#include "zfs_fletcher.h"
 
 #if defined(_KERNEL)
 #include <sys/systm.h>
@@ -695,12 +696,14 @@ zfs_prop_align_right(zfs_prop_t prop)
 static int __init
 zcommon_init(void)
 {
+	fletcher_4_init();
 	return (0);
 }
 
 static void __exit
 zcommon_fini(void)
 {
+	fletcher_4_fini();
 }
 
 module_init(zcommon_init);