Illumos #3035 LZ4 compression support in ZFS and GRUB

3035 LZ4 compression support in ZFS and GRUB

Reviewed by: Matthew Ahrens <[email protected]>
Reviewed by: Christopher Siden <[email protected]>
Reviewed by: George Wilson <[email protected]>
Approved by: Christopher Siden <[email protected]>

References:
  illumos/illumos-gate@a6f561b4aee75d0d028e7b36b151c8ed8a86bc76
  https://www.illumos.org/issues/3035
  http://wiki.illumos.org/display/illumos/LZ4+Compression+In+ZFS

This patch has been slightly modified from the upstream Illumos
version to be compatible with Linux.  Due to the very limited
stack space in the kernel a lz4 workspace kmem cache is used.
Since we are using gcc we are also able to take advantage of the
gcc optimized __builtin_ctz functions.

Support for GRUB has been dropped from this patch.  That code
is available but those changes will need to made to the upstream
GRUB package.

Lastly, several hunks of dead code were dropped for clarity.  They
include the functions real_LZ4_uncompress(), LZ4_compressBound()
and the Visual Studio specific hunks wrapped in _MSC_VER.

Ported-by: Eric Dillmann <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>
Closes #1217

1 files changed, 34 insertions, 0 deletions

diff --git a/man/man5/zpool-features.5 b/man/man5/zpool-features.5
index 0ab179ef7..a306e4388 100644
--- a/man/man5/zpool-features.5
+++ b/man/man5/zpool-features.5
@@ -1,5 +1,6 @@
 '\" te
 .\" Copyright (c) 2012 by Delphix. All rights reserved.
+.\" Copyright (c) 2013 by Saso Kiselkov. All rights reserved.
 .\" The contents of this file are subject to the terms of the Common Development
 .\" and Distribution License (the "License").  You may not use this file except
 .\" in compliance with the License. You can obtain a copy of the license at
@@ -197,5 +198,38 @@ This feature is \fBactive\fR while there are any filesystems, volumes,
 or snapshots which were created after enabling this feature.
 .RE
 
+.sp
+.ne 2
+.na
+\fB\fBlz4_compress\fR\fR
+.ad
+.RS 4n
+.TS
+l l .
+GUID	org.illumos:lz4_compress
+READ\-ONLY COMPATIBLE	no
+DEPENDENCIES	none
+.TE
+
+\fBlz4\fR is a high-performance real-time compression algorithm that
+features significantly faster compression and decompression as well as a
+higher compression ratio than the older \fBlzjb\fR compression.
+Typically, \fBlz4\fR compression is approximately 50% faster on
+compressible data and 200% faster on incompressible data than
+\fBlzjb\fR. It is also approximately 80% faster on decompression, while
+giving approximately 10% better compression ratio.
+
+When the \fBlz4_compress\fR feature is set to \fBenabled\fR, the
+administrator can turn on \fBlz4\fR compression on any dataset on the
+pool using the \fBzfs\fR(1M) command. Please note that doing so will
+immediately activate the \fBlz4_compress\fR feature on the underlying
+pool (even before any data is written). Since this feature is not
+read-only compatible, this operation will render the pool unimportable
+on systems without support for the \fBlz4_compress\fR feature. At the
+moment, this operation cannot be reversed. Booting off of
+\fBlz4\fR-compressed root pools is supported.
+
+.RE
+
 .SH "SEE ALSO"
 \fBzpool\fR(1M)