MFV r245512:

 * Illumos zfs issue #3035 [1] LZ4 compression support in ZFS.

LZ4 is a new high-speed BSD-licensed compression algorithm created
by Yann Collet that delivers very high compression and decompression
performance compared to lzjb (>50% faster on compression, >80% faster
on decompression and around 3x faster on compression of incompressible
data), while giving better compression ratio [1].

This version of LZ4 corresponds to upstream's [2] revision 85.

Please note that for obvious reasons this is not backward read
compatible.  This means once a pool have LZ4 compressed data, these
data can no longer be read by older ZFS implementations.

Local changes:

 - On-stack hash table disabled and using kernel slab allocator
   instead, at this time.  This requires larger kernel thread stack
   for zio workers.  This may change in the future should we adjusted
   the zio workers' thread stack size.
 - likely and unlikely will be undefined if they are already defined,
   this is required for i386 XEN build.
 - Removed De Bruijn sequence based __builtin_ctz family of builtins
   in favor of the latter.  Both GCC and clang supports these builtins.
 - Changed the way the LZ4 code detects endianness.
 - Manual pages modifications to mention the feature based on Illumos
   counterpart.
 - Boot loader changes to make it support LZ4 decompression.

[1] https://www.illumos.org/issues/3035
[2] http://code.google.com/p/lz4/source/list

Obtained from:	Illumos (13921:9d721847e469)
Tested on:	FreeBSD/amd64
MFC after:	1 month

1 files changed, 23 insertions, 2 deletions

diff --git a/cddl/contrib/opensolaris/cmd/zfs/zfs.8 b/cddl/contrib/opensolaris/cmd/zfs/zfs.8
index 3a75681..7b3069d 100644
--- a/cddl/contrib/opensolaris/cmd/zfs/zfs.8
+++ b/cddl/contrib/opensolaris/cmd/zfs/zfs.8
@@ -24,10 +24,11 @@
 .\" Copyright (c) 2011, Pawel Jakub Dawidek <pjd@FreeBSD.org>
 .\" Copyright (c) 2012, Glen Barber <gjb@FreeBSD.org>
 .\" Copyright (c) 2012, Bryan Drewery <bdrewery@FreeBSD.org>
+.\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
 .\"
 .\" $FreeBSD$
 .\"
-.Dd November 26, 2012
+.Dd February 8, 2012
 .Dt ZFS 8
 .Os
 .Sh NAME
@@ -866,7 +867,7 @@ but this may change in future releases). The value
 disables integrity checking on user data. Disabling checksums is
 .Em NOT
 a recommended practice.
-.It Sy compression Ns = Ns Cm on | off | lzjb | gzip | gzip- Ns Ar N | Cm zle
+.It Sy compression Ns = Ns Cm on | off | lzjb | gzip | gzip- Ns Ar N | zle | Cm lz4
 Controls the compression algorithm used for this dataset. The
 .Cm lzjb
 compression algorithm is optimized for performance while providing decent data
@@ -894,6 +895,26 @@ The
 .Cm zle
 compression algorithm compresses runs of zeros.
 .Pp
+The
+.Sy lz4
+compression algorithm is a high-performance replacement
+for the
+.Sy lzjb
+algorithm. It features significantly faster
+compression and decompression, as well as a moderately higher
+compression ratio than
+.Sy lzjb ,
+but can only be used on pools with
+the
+.Sy lz4_compress
+feature set to
+.Sy enabled .
+See
+.Xr zpool-features 7
+for details on ZFS feature flags and the
+.Sy lz4_compress
+feature.
+.Pp
 This property can also be referred to by its shortened column name
 .Cm compress .
 Changing this property affects only newly-written data.