Illumos 5661 - ZFS: "compression = on" should use lz4 if feature is enabled

5661 ZFS: "compression = on" should use lz4 if feature is enabled
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
Reviewed by: Xin LI <delphij@freebsd.org>
Approved by: Robert Mustacchi <rm@joyent.com>

References:
  illumos/illumos-gate@db1741f
  https://www.illumos.org/issues/5661

Ported-by: kernelOfTruth kerneloftruth@gmail.com
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #3571

Author: Justin T. Gibbs

include/sys/zio.h

@@ -123,14 +123,19 @@ enum zio_compress {
  */
 #define	ZIO_COMPRESS_LEGACY_FUNCTIONS ZIO_COMPRESS_LZ4
 
-#define	ZIO_COMPRESS_ON_VALUE	ZIO_COMPRESS_LZJB
-#define	ZIO_COMPRESS_DEFAULT	ZIO_COMPRESS_OFF
+/*
+ * The meaning of "compress = on" selected by the compression features enabled
+ * on a given pool.
+ */
+#define	ZIO_COMPRESS_LEGACY_ON_VALUE	ZIO_COMPRESS_LZJB
+#define	ZIO_COMPRESS_LZ4_ON_VALUE	ZIO_COMPRESS_LZ4
+
+#define	ZIO_COMPRESS_DEFAULT		ZIO_COMPRESS_OFF
 
 #define	BOOTFS_COMPRESS_VALID(compress)			\
 	((compress) == ZIO_COMPRESS_LZJB ||		\
 	(compress) == ZIO_COMPRESS_LZ4 ||		\
-	((compress) == ZIO_COMPRESS_ON &&		\
-	ZIO_COMPRESS_ON_VALUE == ZIO_COMPRESS_LZJB) ||	\
+	(compress) == ZIO_COMPRESS_ON ||		\
 	(compress) == ZIO_COMPRESS_OFF)
 
 /*
@@ -543,8 +548,8 @@ extern enum zio_checksum zio_checksum_select(enum zio_checksum child,
     enum zio_checksum parent);
 extern enum zio_checksum zio_checksum_dedup_select(spa_t *spa,
     enum zio_checksum child, enum zio_checksum parent);
-extern enum zio_compress zio_compress_select(enum zio_compress child,
-    enum zio_compress parent);
+extern enum zio_compress zio_compress_select(spa_t *spa,
+    enum zio_compress child, enum zio_compress parent);
 
 extern void zio_suspend(spa_t *spa, zio_t *zio);
 extern int zio_resume(spa_t *spa);

man/man8/zfs.8

@@ -840,15 +840,25 @@ Changing this property affects only newly-written data.
 .ne 2
 .mk
 .na
-\fBcompression\fR=\fBon\fR | \fBoff\fR | \fBlzjb\fR | \fBgzip\fR | \fBgzip-\fR\fIN\fR | \fBzle\fR | \fBlz4\fR
+\fB\fBcompression\fR=\fBon\fR | \fBoff\fR | \fBlzjb\fR | \fBlz4\fR |
+\fBgzip\fR | \fBgzip-\fR\fIN\fR | \fBzle\fR\fR
 .ad
 .sp .6
 .RS 4n
-Controls the compression algorithm used for this dataset. The \fBlzjb\fR compression algorithm is optimized for performance while providing decent data compression. Setting compression to \fBon\fR uses the \fBlzjb\fR compression algorithm.
+Controls the compression algorithm used for this dataset.
 .sp
-The \fBgzip\fR compression algorithm uses the same compression as the \fBgzip\fR(1) command. You can specify the \fBgzip\fR level by using the value \fBgzip-\fR\fIN\fR where \fIN\fR is an integer from 1 (fastest) to 9 (best compression ratio). Currently, \fBgzip\fR is equivalent to \fBgzip-6\fR (which is also the default for \fBgzip\fR(1)).
+Setting compression to \fBon\fR indicates that the current default
+compression algorithm should be used.  The default balances compression
+and decompression speed, with compression ratio and is expected to
+work well on a wide variety of workloads.  Unlike all other settings for
+this property, \fBon\fR does not select a fixed compression type.  As
+new compression algorithms are added to ZFS and enabled on a pool, the
+default compression algorithm may change.  The current default compression
+algorthm is either \fBlzjb\fR or, if the \fBlz4_compress\fR feature is
+enabled, \fBlz4\fR.
 .sp
-The \fBzle\fR (zero-length encoding) compression algorithm is a fast and simple algorithm to eliminate runs of zeroes.
+The \fBlzjb\fR compression algorithm is optimized for performance while
+providing decent data compression.
 .sp
 The \fBlz4\fR compression algorithm is a high-performance replacement
 for the \fBlzjb\fR algorithm. It features significantly faster
@@ -858,7 +868,15 @@ the \fBlz4_compress\fR feature set to \fIenabled\fR. See
 \fBzpool-features\fR(5) for details on ZFS feature flags and the
 \fBlz4_compress\fR feature.
 .sp
-This property can also be referred to by its shortened column name \fBcompress\fR. Changing this property affects only newly-written data.
+The \fBgzip\fR compression algorithm uses the same compression as
+the \fBgzip\fR(1) command. You can specify the \fBgzip\fR level by using the
+value \fBgzip-\fR\fIN\fR where \fIN\fR is an integer from 1 (fastest) to 9
+(best compression ratio). Currently, \fBgzip\fR is equivalent to \fBgzip-6\fR
+(which is also the default for \fBgzip\fR(1)). The \fBzle\fR compression
+algorithm compresses runs of zeros.
+.sp
+This property can also be referred to by its shortened column name
+\fBcompress\fR. Changing this property affects only newly-written data.
 .RE
 
 .sp

module/zfs/dmu.c

@@ -1864,19 +1864,15 @@ dmu_write_policy(objset_t *os, dnode_t *dn, int level, int wp, zio_prop_t *zp)
 	 *	 3. all other level 0 blocks
 	 */
 	if (ismd) {
-		/*
-		 * XXX -- we should design a compression algorithm
-		 * that specializes in arrays of bps.
-		 */
-		boolean_t lz4_ac = spa_feature_is_active(os->os_spa,
-		    SPA_FEATURE_LZ4_COMPRESS);
-
 		if (zfs_mdcomp_disable) {
 			compress = ZIO_COMPRESS_EMPTY;
-		} else if (lz4_ac) {
-			compress = ZIO_COMPRESS_LZ4;
 		} else {
-			compress = ZIO_COMPRESS_LZJB;
+			/*
+			 * XXX -- we should design a compression algorithm
+			 * that specializes in arrays of bps.
+			 */
+			compress = zio_compress_select(os->os_spa,
+			    ZIO_COMPRESS_ON, ZIO_COMPRESS_ON);
 		}
 
 		/*
@@ -1909,7 +1905,8 @@ dmu_write_policy(objset_t *os, dnode_t *dn, int level, int wp, zio_prop_t *zp)
 		compress = ZIO_COMPRESS_OFF;
 		checksum = ZIO_CHECKSUM_OFF;
 	} else {
-		compress = zio_compress_select(dn->dn_compress, compress);
+		compress = zio_compress_select(os->os_spa, dn->dn_compress,
+		    compress);
 
 		checksum = (dedup_checksum == ZIO_CHECKSUM_OFF) ?
 		    zio_checksum_select(dn->dn_checksum, checksum) :

module/zfs/dmu_objset.c

@@ -163,7 +163,8 @@ compression_changed_cb(void *arg, uint64_t newval)
 	 */
 	ASSERT(newval != ZIO_COMPRESS_INHERIT);
 
-	os->os_compress = zio_compress_select(newval, ZIO_COMPRESS_ON_VALUE);
+	os->os_compress = zio_compress_select(os->os_spa, newval,
+	    ZIO_COMPRESS_ON);
 }
 
 static void
@@ -420,7 +421,7 @@ dmu_objset_open_impl(spa_t *spa, dsl_dataset_t *ds, blkptr_t *bp,
 	} else {
 		/* It's the meta-objset. */
 		os->os_checksum = ZIO_CHECKSUM_FLETCHER_4;
-		os->os_compress = ZIO_COMPRESS_LZJB;
+		os->os_compress = ZIO_COMPRESS_ON;
 		os->os_copies = spa_max_replication(spa);
 		os->os_dedup_checksum = ZIO_CHECKSUM_OFF;
 		os->os_dedup_verify = B_FALSE;

module/zfs/zio_compress.c

@@ -34,6 +34,7 @@
 #include <sys/zfs_context.h>
 #include <sys/compress.h>
 #include <sys/spa.h>
+#include <sys/zfeature.h>
 #include <sys/zio.h>
 #include <sys/zio_compress.h>
 
@@ -61,19 +62,27 @@ zio_compress_info_t zio_compress_table[ZIO_COMPRESS_FUNCTIONS] = {
 };
 
 enum zio_compress
-zio_compress_select(enum zio_compress child, enum zio_compress parent)
+zio_compress_select(spa_t *spa, enum zio_compress child,
+    enum zio_compress parent)
 {
+	enum zio_compress result;
+
 	ASSERT(child < ZIO_COMPRESS_FUNCTIONS);
 	ASSERT(parent < ZIO_COMPRESS_FUNCTIONS);
-	ASSERT(parent != ZIO_COMPRESS_INHERIT && parent != ZIO_COMPRESS_ON);
+	ASSERT(parent != ZIO_COMPRESS_INHERIT);
 
-	if (child == ZIO_COMPRESS_INHERIT)
-		return (parent);
+	result = child;
+	if (result == ZIO_COMPRESS_INHERIT)
+		result = parent;
 
-	if (child == ZIO_COMPRESS_ON)
-		return (ZIO_COMPRESS_ON_VALUE);
+	if (result == ZIO_COMPRESS_ON) {
+		if (spa_feature_is_active(spa, SPA_FEATURE_LZ4_COMPRESS))
+			result = ZIO_COMPRESS_LZ4_ON_VALUE;
+		else
+			result = ZIO_COMPRESS_LEGACY_ON_VALUE;
+	}
 
-	return (child);
+	return (result);
 }
 
 size_t