Re: [PATCH v3 0/4] Add xxhash and zstd modules

2017-07-24 Thread Austin S. Hemmelgarn 

On 2017-07-22 07:35, Adam Borowski wrote:

On Fri, Jul 21, 2017 at 11:56:21AM -0400, Austin S. Hemmelgarn wrote:

On 2017-07-20 17:27, Nick Terrell wrote:

This patch set adds xxhash, zstd compression, and zstd decompression
modules. It also adds zstd support to BtrFS and SquashFS.

Each patch has relevant summaries, benchmarks, and tests.


For patches 2-3, I've compile tested and had runtime testing running for
about 18 hours now with no issues, so you can add:

Tested-by: Austin S. Hemmelgarn 


I assume you haven't tried it on arm64, right?

I had no time to get 'round to it before, and just got the following build
failure:

   CC  fs/btrfs/zstd.o
In file included from fs/btrfs/zstd.c:28:0:
fs/btrfs/compression.h:39:2: error: unknown type name ‘refcount_t’
   refcount_t pending_bios;
   ^~
scripts/Makefile.build:302: recipe for target 'fs/btrfs/zstd.o' failed

It's trivially fixably by:
--- a/fs/btrfs/zstd.c
+++ b/fs/btrfs/zstd.c
@@ -24,6 +24,7 @@
  #include 
  #include 
  #include 
+#include 
  #include 
  #include "compression.h"

after which it works fine, although half an hour of testing isn't exactly
exhaustive.

I did, and didn't hit this somehow...

Off to go verify my tool-chain and scripts then...



Alas, the armhf machine I ran stress tests (Debian archive rebuilds) on
doesn't boot with 4.13-rc1 due to some unrelated regression, bisecting that
would be quite painful so I did not try yet.  I guess re-testing your patch
set on 4.12, even with btrfs-for-4.13 (which it had for a while), wouldn't
be of much help.  So far, previous versions have been running for weeks,
with no issue since you fixed workspace flickering.
I also didn't see this, but I test on some seriously bare-bones 
configurations for both the 32-bit ARM tests I run.  On further 
inspection, it looks like my scripts decided to use btrfs-for-4.13 as 
the base, not 4.13-rc1 like I thought they did, so I don't know anymore 
how helpful my testing may have been.



On amd64 all is fine.


I haven't tested SquashFS at all.


Meow!



--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH v3 0/4] Add xxhash and zstd modules

2017-07-22 Thread Adam Borowski 
On Fri, Jul 21, 2017 at 11:56:21AM -0400, Austin S. Hemmelgarn wrote:
> On 2017-07-20 17:27, Nick Terrell wrote:
> > This patch set adds xxhash, zstd compression, and zstd decompression
> > modules. It also adds zstd support to BtrFS and SquashFS.
> > 
> > Each patch has relevant summaries, benchmarks, and tests.
> 
> For patches 2-3, I've compile tested and had runtime testing running for
> about 18 hours now with no issues, so you can add:
> 
> Tested-by: Austin S. Hemmelgarn 

I assume you haven't tried it on arm64, right?

I had no time to get 'round to it before, and just got the following build
failure:

  CC  fs/btrfs/zstd.o
In file included from fs/btrfs/zstd.c:28:0:
fs/btrfs/compression.h:39:2: error: unknown type name ‘refcount_t’
  refcount_t pending_bios;
  ^~
scripts/Makefile.build:302: recipe for target 'fs/btrfs/zstd.o' failed

It's trivially fixably by:
--- a/fs/btrfs/zstd.c
+++ b/fs/btrfs/zstd.c
@@ -24,6 +24,7 @@
 #include 
 #include 
 #include 
+#include 
 #include 
 #include "compression.h"

after which it works fine, although half an hour of testing isn't exactly
exhaustive.


Alas, the armhf machine I ran stress tests (Debian archive rebuilds) on
doesn't boot with 4.13-rc1 due to some unrelated regression, bisecting that
would be quite painful so I did not try yet.  I guess re-testing your patch
set on 4.12, even with btrfs-for-4.13 (which it had for a while), wouldn't
be of much help.  So far, previous versions have been running for weeks,
with no issue since you fixed workspace flickering.


On amd64 all is fine.


I haven't tested SquashFS at all.


Meow!
-- 
⢀⣴⠾⠻⢶⣦⠀ 
⣾⠁⢠⠒⠀⣿⡁ A dumb species has no way to open a tuna can.
⢿⡄⠘⠷⠚⠋⠀ A smart species invents a can opener.
⠈⠳⣄ A master species delegates.
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH v3 0/4] Add xxhash and zstd modules

2017-07-21 Thread Austin S. Hemmelgarn 

On 2017-07-20 17:27, Nick Terrell wrote:

Hi all,

This patch set adds xxhash, zstd compression, and zstd decompression
modules. It also adds zstd support to BtrFS and SquashFS.

Each patch has relevant summaries, benchmarks, and tests.

Best,
Nick Terrell


For patches 2-3, I've compile tested and had runtime testing running for 
about 18 hours now with no issues, so you can add:


Tested-by: Austin S. Hemmelgarn 

For patch 1, I've only compile tested it, but had no issues and got no 
warnings about it when booting to test 2-4.


For patch 4, I've compile tested it and done some really basic runtime 
testing using a couple of hand-crafted SquashFS images.  It appears to 
run fine, but I've not done enough that I feel it warrants a Tested-by 
tag from me.


Changelog:

v1 -> v2:
- Make pointer in lib/xxhash.c:394 non-const (1/4)
- Use div_u64() for division of u64s (2/4)
- Reduce stack usage of ZSTD_compressSequences(), ZSTD_buildSeqTable(),
   ZSTD_decompressSequencesLong(), FSE_buildDTable(), FSE_decompress_wksp(),
   HUF_writeCTable(), HUF_readStats(), HUF_readCTable(),
   HUF_compressWeights(), HUF_readDTableX2(), and HUF_readDTableX4() (2/4)
- No zstd function uses more than 400 B of stack space (2/4)

v2 -> v3:
- Work around gcc-7 bug https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81388
   (2/4)
- Fix bug in dictionary compression from upstream commit cc1522351f (2/4)
- Port upstream BtrFS commits e1ddce71d6, 389a6cfc2a, and 6acafd1eff (3/4)
- Change default compression level for BtrFS to 3 (3/4)

Nick Terrell (4):
   lib: Add xxhash module
   lib: Add zstd modules
   btrfs: Add zstd support
   squashfs: Add zstd support

  fs/btrfs/Kconfig   |2 +
  fs/btrfs/Makefile  |2 +-
  fs/btrfs/compression.c |1 +
  fs/btrfs/compression.h |6 +-
  fs/btrfs/ctree.h   |1 +
  fs/btrfs/disk-io.c |2 +
  fs/btrfs/ioctl.c   |6 +-
  fs/btrfs/props.c   |6 +
  fs/btrfs/super.c   |   12 +-
  fs/btrfs/sysfs.c   |2 +
  fs/btrfs/zstd.c|  435 ++
  fs/squashfs/Kconfig|   14 +
  fs/squashfs/Makefile   |1 +
  fs/squashfs/decompressor.c |7 +
  fs/squashfs/decompressor.h |4 +
  fs/squashfs/squashfs_fs.h  |1 +
  fs/squashfs/zstd_wrapper.c |  150 ++
  include/linux/xxhash.h |  236 +++
  include/linux/zstd.h   | 1157 +++
  include/uapi/linux/btrfs.h |8 +-
  lib/Kconfig|   11 +
  lib/Makefile   |3 +
  lib/xxhash.c   |  500 +++
  lib/zstd/Makefile  |   18 +
  lib/zstd/bitstream.h   |  374 +
  lib/zstd/compress.c| 3479 
  lib/zstd/decompress.c  | 2526 
  lib/zstd/entropy_common.c  |  243 
  lib/zstd/error_private.h   |   53 +
  lib/zstd/fse.h |  575 
  lib/zstd/fse_compress.c|  795 ++
  lib/zstd/fse_decompress.c  |  332 +
  lib/zstd/huf.h |  212 +++
  lib/zstd/huf_compress.c|  770 ++
  lib/zstd/huf_decompress.c  |  960 
  lib/zstd/mem.h |  151 ++
  lib/zstd/zstd_common.c |   75 +
  lib/zstd/zstd_internal.h   |  250 
  lib/zstd/zstd_opt.h| 1014 +
  39 files changed, 14382 insertions(+), 12 deletions(-)
  create mode 100644 fs/btrfs/zstd.c
  create mode 100644 fs/squashfs/zstd_wrapper.c
  create mode 100644 include/linux/xxhash.h
  create mode 100644 include/linux/zstd.h
  create mode 100644 lib/xxhash.c
  create mode 100644 lib/zstd/Makefile
  create mode 100644 lib/zstd/bitstream.h
  create mode 100644 lib/zstd/compress.c
  create mode 100644 lib/zstd/decompress.c
  create mode 100644 lib/zstd/entropy_common.c
  create mode 100644 lib/zstd/error_private.h
  create mode 100644 lib/zstd/fse.h
  create mode 100644 lib/zstd/fse_compress.c
  create mode 100644 lib/zstd/fse_decompress.c
  create mode 100644 lib/zstd/huf.h
  create mode 100644 lib/zstd/huf_compress.c
  create mode 100644 lib/zstd/huf_decompress.c
  create mode 100644 lib/zstd/mem.h
  create mode 100644 lib/zstd/zstd_common.c
  create mode 100644 lib/zstd/zstd_internal.h
  create mode 100644 lib/zstd/zstd_opt.h

--
2.9.3



--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH v3 0/4] Add xxhash and zstd modules

2017-07-21 Thread Austin S. Hemmelgarn 

On 2017-07-21 07:16, Austin S. Hemmelgarn wrote:

On 2017-07-20 17:27, Nick Terrell wrote:

Well this is embarrassing, forgot to type anything before hitting send...

Hi all,

This patch set adds xxhash, zstd compression, and zstd decompression
modules. It also adds zstd support to BtrFS and SquashFS.

Each patch has relevant summaries, benchmarks, and tests.

Best,
Nick Terrell
I've compile tested all of this on my end now, and have gotten some 
preliminary testing of patches 2-4, and everything looks good so far 
here.  I'll reply to this if I end up finding issues, but it doesn't 
look like I will right now considering the testing has run over night 
without issue.


Changelog:

v1 -> v2:
- Make pointer in lib/xxhash.c:394 non-const (1/4)
- Use div_u64() for division of u64s (2/4)
- Reduce stack usage of ZSTD_compressSequences(), ZSTD_buildSeqTable(),
   ZSTD_decompressSequencesLong(), FSE_buildDTable(), 
FSE_decompress_wksp(),

   HUF_writeCTable(), HUF_readStats(), HUF_readCTable(),
   HUF_compressWeights(), HUF_readDTableX2(), and HUF_readDTableX4() 
(2/4)

- No zstd function uses more than 400 B of stack space (2/4)

v2 -> v3:
- Work around gcc-7 bug 
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81388

   (2/4)
- Fix bug in dictionary compression from upstream commit cc1522351f (2/4)
- Port upstream BtrFS commits e1ddce71d6, 389a6cfc2a, and 6acafd1eff 
(3/4)

- Change default compression level for BtrFS to 3 (3/4)

Nick Terrell (4):
   lib: Add xxhash module
   lib: Add zstd modules
   btrfs: Add zstd support
   squashfs: Add zstd support

  fs/btrfs/Kconfig   |2 +
  fs/btrfs/Makefile  |2 +-
  fs/btrfs/compression.c |1 +
  fs/btrfs/compression.h |6 +-
  fs/btrfs/ctree.h   |1 +
  fs/btrfs/disk-io.c |2 +
  fs/btrfs/ioctl.c   |6 +-
  fs/btrfs/props.c   |6 +
  fs/btrfs/super.c   |   12 +-
  fs/btrfs/sysfs.c   |2 +
  fs/btrfs/zstd.c|  435 ++
  fs/squashfs/Kconfig|   14 +
  fs/squashfs/Makefile   |1 +
  fs/squashfs/decompressor.c |7 +
  fs/squashfs/decompressor.h |4 +
  fs/squashfs/squashfs_fs.h  |1 +
  fs/squashfs/zstd_wrapper.c |  150 ++
  include/linux/xxhash.h |  236 +++
  include/linux/zstd.h   | 1157 +++
  include/uapi/linux/btrfs.h |8 +-
  lib/Kconfig|   11 +
  lib/Makefile   |3 +
  lib/xxhash.c   |  500 +++
  lib/zstd/Makefile  |   18 +
  lib/zstd/bitstream.h   |  374 +
  lib/zstd/compress.c| 3479 


  lib/zstd/decompress.c  | 2526 
  lib/zstd/entropy_common.c  |  243 
  lib/zstd/error_private.h   |   53 +
  lib/zstd/fse.h |  575 
  lib/zstd/fse_compress.c|  795 ++
  lib/zstd/fse_decompress.c  |  332 +
  lib/zstd/huf.h |  212 +++
  lib/zstd/huf_compress.c|  770 ++
  lib/zstd/huf_decompress.c  |  960 
  lib/zstd/mem.h |  151 ++
  lib/zstd/zstd_common.c |   75 +
  lib/zstd/zstd_internal.h   |  250 
  lib/zstd/zstd_opt.h| 1014 +
  39 files changed, 14382 insertions(+), 12 deletions(-)
  create mode 100644 fs/btrfs/zstd.c
  create mode 100644 fs/squashfs/zstd_wrapper.c
  create mode 100644 include/linux/xxhash.h
  create mode 100644 include/linux/zstd.h
  create mode 100644 lib/xxhash.c
  create mode 100644 lib/zstd/Makefile
  create mode 100644 lib/zstd/bitstream.h
  create mode 100644 lib/zstd/compress.c
  create mode 100644 lib/zstd/decompress.c
  create mode 100644 lib/zstd/entropy_common.c
  create mode 100644 lib/zstd/error_private.h
  create mode 100644 lib/zstd/fse.h
  create mode 100644 lib/zstd/fse_compress.c
  create mode 100644 lib/zstd/fse_decompress.c
  create mode 100644 lib/zstd/huf.h
  create mode 100644 lib/zstd/huf_compress.c
  create mode 100644 lib/zstd/huf_decompress.c
  create mode 100644 lib/zstd/mem.h
  create mode 100644 lib/zstd/zstd_common.c
  create mode 100644 lib/zstd/zstd_internal.h
  create mode 100644 lib/zstd/zstd_opt.h

--
2.9.3





--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: [PATCH v3 0/4] Add xxhash and zstd modules

2017-07-21 Thread Austin S. Hemmelgarn 

On 2017-07-20 17:27, Nick Terrell wrote:

Hi all,

This patch set adds xxhash, zstd compression, and zstd decompression
modules. It also adds zstd support to BtrFS and SquashFS.

Each patch has relevant summaries, benchmarks, and tests.

Best,
Nick Terrell

Changelog:

v1 -> v2:
- Make pointer in lib/xxhash.c:394 non-const (1/4)
- Use div_u64() for division of u64s (2/4)
- Reduce stack usage of ZSTD_compressSequences(), ZSTD_buildSeqTable(),
   ZSTD_decompressSequencesLong(), FSE_buildDTable(), FSE_decompress_wksp(),
   HUF_writeCTable(), HUF_readStats(), HUF_readCTable(),
   HUF_compressWeights(), HUF_readDTableX2(), and HUF_readDTableX4() (2/4)
- No zstd function uses more than 400 B of stack space (2/4)

v2 -> v3:
- Work around gcc-7 bug https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81388
   (2/4)
- Fix bug in dictionary compression from upstream commit cc1522351f (2/4)
- Port upstream BtrFS commits e1ddce71d6, 389a6cfc2a, and 6acafd1eff (3/4)
- Change default compression level for BtrFS to 3 (3/4)

Nick Terrell (4):
   lib: Add xxhash module
   lib: Add zstd modules
   btrfs: Add zstd support
   squashfs: Add zstd support

  fs/btrfs/Kconfig   |2 +
  fs/btrfs/Makefile  |2 +-
  fs/btrfs/compression.c |1 +
  fs/btrfs/compression.h |6 +-
  fs/btrfs/ctree.h   |1 +
  fs/btrfs/disk-io.c |2 +
  fs/btrfs/ioctl.c   |6 +-
  fs/btrfs/props.c   |6 +
  fs/btrfs/super.c   |   12 +-
  fs/btrfs/sysfs.c   |2 +
  fs/btrfs/zstd.c|  435 ++
  fs/squashfs/Kconfig|   14 +
  fs/squashfs/Makefile   |1 +
  fs/squashfs/decompressor.c |7 +
  fs/squashfs/decompressor.h |4 +
  fs/squashfs/squashfs_fs.h  |1 +
  fs/squashfs/zstd_wrapper.c |  150 ++
  include/linux/xxhash.h |  236 +++
  include/linux/zstd.h   | 1157 +++
  include/uapi/linux/btrfs.h |8 +-
  lib/Kconfig|   11 +
  lib/Makefile   |3 +
  lib/xxhash.c   |  500 +++
  lib/zstd/Makefile  |   18 +
  lib/zstd/bitstream.h   |  374 +
  lib/zstd/compress.c| 3479 
  lib/zstd/decompress.c  | 2526 
  lib/zstd/entropy_common.c  |  243 
  lib/zstd/error_private.h   |   53 +
  lib/zstd/fse.h |  575 
  lib/zstd/fse_compress.c|  795 ++
  lib/zstd/fse_decompress.c  |  332 +
  lib/zstd/huf.h |  212 +++
  lib/zstd/huf_compress.c|  770 ++
  lib/zstd/huf_decompress.c  |  960 
  lib/zstd/mem.h |  151 ++
  lib/zstd/zstd_common.c |   75 +
  lib/zstd/zstd_internal.h   |  250 
  lib/zstd/zstd_opt.h| 1014 +
  39 files changed, 14382 insertions(+), 12 deletions(-)
  create mode 100644 fs/btrfs/zstd.c
  create mode 100644 fs/squashfs/zstd_wrapper.c
  create mode 100644 include/linux/xxhash.h
  create mode 100644 include/linux/zstd.h
  create mode 100644 lib/xxhash.c
  create mode 100644 lib/zstd/Makefile
  create mode 100644 lib/zstd/bitstream.h
  create mode 100644 lib/zstd/compress.c
  create mode 100644 lib/zstd/decompress.c
  create mode 100644 lib/zstd/entropy_common.c
  create mode 100644 lib/zstd/error_private.h
  create mode 100644 lib/zstd/fse.h
  create mode 100644 lib/zstd/fse_compress.c
  create mode 100644 lib/zstd/fse_decompress.c
  create mode 100644 lib/zstd/huf.h
  create mode 100644 lib/zstd/huf_compress.c
  create mode 100644 lib/zstd/huf_decompress.c
  create mode 100644 lib/zstd/mem.h
  create mode 100644 lib/zstd/zstd_common.c
  create mode 100644 lib/zstd/zstd_internal.h
  create mode 100644 lib/zstd/zstd_opt.h

--
2.9.3



--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

[PATCH v3 0/4] Add xxhash and zstd modules

2017-07-20 Thread Nick Terrell 
Hi all,

This patch set adds xxhash, zstd compression, and zstd decompression
modules. It also adds zstd support to BtrFS and SquashFS.

Each patch has relevant summaries, benchmarks, and tests.

Best,
Nick Terrell

Changelog:

v1 -> v2:
- Make pointer in lib/xxhash.c:394 non-const (1/4)
- Use div_u64() for division of u64s (2/4)
- Reduce stack usage of ZSTD_compressSequences(), ZSTD_buildSeqTable(),
  ZSTD_decompressSequencesLong(), FSE_buildDTable(), FSE_decompress_wksp(),
  HUF_writeCTable(), HUF_readStats(), HUF_readCTable(),
  HUF_compressWeights(), HUF_readDTableX2(), and HUF_readDTableX4() (2/4)
- No zstd function uses more than 400 B of stack space (2/4)

v2 -> v3:
- Work around gcc-7 bug https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81388
  (2/4)
- Fix bug in dictionary compression from upstream commit cc1522351f (2/4)
- Port upstream BtrFS commits e1ddce71d6, 389a6cfc2a, and 6acafd1eff (3/4)
- Change default compression level for BtrFS to 3 (3/4)

Nick Terrell (4):
  lib: Add xxhash module
  lib: Add zstd modules
  btrfs: Add zstd support
  squashfs: Add zstd support

 fs/btrfs/Kconfig   |2 +
 fs/btrfs/Makefile  |2 +-
 fs/btrfs/compression.c |1 +
 fs/btrfs/compression.h |6 +-
 fs/btrfs/ctree.h   |1 +
 fs/btrfs/disk-io.c |2 +
 fs/btrfs/ioctl.c   |6 +-
 fs/btrfs/props.c   |6 +
 fs/btrfs/super.c   |   12 +-
 fs/btrfs/sysfs.c   |2 +
 fs/btrfs/zstd.c|  435 ++
 fs/squashfs/Kconfig|   14 +
 fs/squashfs/Makefile   |1 +
 fs/squashfs/decompressor.c |7 +
 fs/squashfs/decompressor.h |4 +
 fs/squashfs/squashfs_fs.h  |1 +
 fs/squashfs/zstd_wrapper.c |  150 ++
 include/linux/xxhash.h |  236 +++
 include/linux/zstd.h   | 1157 +++
 include/uapi/linux/btrfs.h |8 +-
 lib/Kconfig|   11 +
 lib/Makefile   |3 +
 lib/xxhash.c   |  500 +++
 lib/zstd/Makefile  |   18 +
 lib/zstd/bitstream.h   |  374 +
 lib/zstd/compress.c| 3479 
 lib/zstd/decompress.c  | 2526 
 lib/zstd/entropy_common.c  |  243 
 lib/zstd/error_private.h   |   53 +
 lib/zstd/fse.h |  575 
 lib/zstd/fse_compress.c|  795 ++
 lib/zstd/fse_decompress.c  |  332 +
 lib/zstd/huf.h |  212 +++
 lib/zstd/huf_compress.c|  770 ++
 lib/zstd/huf_decompress.c  |  960 
 lib/zstd/mem.h |  151 ++
 lib/zstd/zstd_common.c |   75 +
 lib/zstd/zstd_internal.h   |  250 
 lib/zstd/zstd_opt.h| 1014 +
 39 files changed, 14382 insertions(+), 12 deletions(-)
 create mode 100644 fs/btrfs/zstd.c
 create mode 100644 fs/squashfs/zstd_wrapper.c
 create mode 100644 include/linux/xxhash.h
 create mode 100644 include/linux/zstd.h
 create mode 100644 lib/xxhash.c
 create mode 100644 lib/zstd/Makefile
 create mode 100644 lib/zstd/bitstream.h
 create mode 100644 lib/zstd/compress.c
 create mode 100644 lib/zstd/decompress.c
 create mode 100644 lib/zstd/entropy_common.c
 create mode 100644 lib/zstd/error_private.h
 create mode 100644 lib/zstd/fse.h
 create mode 100644 lib/zstd/fse_compress.c
 create mode 100644 lib/zstd/fse_decompress.c
 create mode 100644 lib/zstd/huf.h
 create mode 100644 lib/zstd/huf_compress.c
 create mode 100644 lib/zstd/huf_decompress.c
 create mode 100644 lib/zstd/mem.h
 create mode 100644 lib/zstd/zstd_common.c
 create mode 100644 lib/zstd/zstd_internal.h
 create mode 100644 lib/zstd/zstd_opt.h

--
2.9.3
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html