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, 20 insertions, 1 deletions

diff --git a/include/zfs_fletcher.h b/include/zfs_fletcher.h
index b49df0cf4..4ccb4a2f4 100644
--- a/include/zfs_fletcher.h
+++ b/include/zfs_fletcher.h
@@ -27,7 +27,7 @@
 #define	_ZFS_FLETCHER_H
 
 #include <sys/types.h>
-#include <sys/spa.h>
+#include <sys/spa_checksum.h>
 
 #ifdef	__cplusplus
 extern "C" {
@@ -45,6 +45,25 @@ void fletcher_4_incremental_native(const void *, uint64_t,
     zio_cksum_t *);
 void fletcher_4_incremental_byteswap(const void *, uint64_t,
     zio_cksum_t *);
+int fletcher_4_impl_set(const char *selector);
+void fletcher_4_init(void);
+void fletcher_4_fini(void);
+
+/*
+ * fletcher checksum struct
+ */
+typedef struct fletcher_4_func {
+	void (*init)(zio_cksum_t *);
+	void (*fini)(zio_cksum_t *);
+	void (*compute)(const void *, uint64_t, zio_cksum_t *);
+	void (*compute_byteswap)(const void *, uint64_t, zio_cksum_t *);
+	boolean_t (*valid)(void);
+	const char *name;
+} fletcher_4_ops_t;
+
+#if defined(HAVE_AVX) && defined(HAVE_AVX2)
+extern const fletcher_4_ops_t fletcher_4_avx2_ops;
+#endif
 
 #ifdef	__cplusplus
 }