GNU bug report logs - #35438
[PATCH v2] Document IBM Z environment variables

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Jim Meyering <jim <at> meyering.net>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#35438: closed ([PATCH v2] Document IBM Z environment variables)
Date: Sun, 05 Jan 2020 21:57:02 +0000

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Your message dated Sun, 5 Jan 2020 13:55:45 -0800
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and subject line Re: Document IBM Z environment variables
has caused the debbugs.gnu.org bug report #35438,
regarding [PATCH v2] Document IBM Z environment variables
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From: Ilya Leoshkevich <iii <at> linux.ibm.com>
To: bug-gzip <at> gnu.org
Cc: Ilya Leoshkevich <iii <at> linux.ibm.com>
Subject: [PATCH v2] Document IBM Z environment variables
Date: Fri, 26 Apr 2019 16:32:22 +0200

Hello,

I realized I forgot to document SOURCE_DATE_EPOCH.
This new patch adds the description for this environment variable.

Best regards,
Ilya

---

IBM Z patch (7a6f9c9) introduced 6 environment variables, which are
used to tune the compression and decompression with the DEFLATE
COMPRESSION CALL instruction.  This patch adds texinfo documentation for
all of them.

* doc/gzip.texi(Environment): Add DFLTCC* environment variables.
---
 doc/gzip.texi | 44 +++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 43 insertions(+), 1 deletion(-)

diff --git a/doc/gzip.texi b/doc/gzip.texi
index a6d9896..fd2075d 100644
--- a/doc/gzip.texi
+++ b/doc/gzip.texi
@@ -69,7 +69,7 @@ Free Documentation License''.
 * Sample::		Sample output from @command{gzip}.
 * Invoking gzip::	How to run @command{gzip}.
 * Advanced usage::	Concatenated files.
-* Environment::		The @env{GZIP} environment variable
+* Environment::		Environment variables.
 * Tapes::               Using @command{gzip} on tapes.
 * Problems::		Reporting bugs.
 * GNU Free Documentation License:: Copying and sharing this manual.
@@ -513,6 +513,48 @@ export PATH=/usr/bin
 exec gzip -9 "$@@"
 @end example
 
+The following environment variables are applicable only when using
+@command{gzip} on IBM Z mainframes supporting DEFLATE COMPRESSION CALL
+instruction:
+
+@table @option
+
+@item DFLTCC
+Whether DEFLATE COMPRESSION CALL should be used.  Default value is @samp{1}.
+Set this to @samp{0} to disable DEFLATE COMPRESSION CALL altogether.
+
+@item DFLTCC_LEVEL_MASK
+Compression levels on which DEFLATE COMPRESSION CALL should be used.
+Represented as a bit mask in decimal or hexadecimal form, where each bit
+corresponds to a compression level.  Default value is @samp{2}, which means
+level 1 only.  In order to make use of DEFLATE COMPRESSION CALL by default, that
+is, on levels 1-6, set this to @samp{0x7e}.
+
+@item DFLTCC_BLOCK_SIZE
+Size of deflate blocks produced by DEFLATE COMPRESSION CALL in bytes in decimal
+or hexadecimal form.  Default value is @samp{1048576} (1 megabyte).  When using
+DEFLATE COMPRESSION CALL to compress a file containing heterogeneous data (e.g.
+a @samp{.tar} archive containing text and binary files), setting this to a
+smaller value may improve compression ratio.
+
+@item DFLTCC_FIRST_FHT_BLOCK_SIZE
+Size of the first fixed deflate block produced by DEFLATE COMPRESSION CALL in
+bytes in decimal or hexadecimal form.  Default value is @samp{4096} (4
+kilobytes).  When using DEFLATE COMPRESSION CALL to compress a small file,
+setting this to a larger value may improve compression ratio.
+
+@item DFLTCC_RIBM
+Value of "Reserved for IBM" field of DEFLATE COMPRESSION CALL parameter block.
+Default value is @samp{0}.
+
+@item SOURCE_DATE_EPOCH
+If set to any value, disables compression with DEFLATE COMPRESSION CALL.  This
+variable is normally set during reproducible builds, and in such cases DEFLATE
+COMPRESSION CALL needs to be disabled, because its output may be not
+reproducible.
+
+@end table
+
 @node Tapes
 @chapter Using @command{gzip} on tapes
 @cindex tapes
-- 
2.21.0

[Message part 3 (message/rfc822, inline)]

From: Jim Meyering <jim <at> meyering.net>
To: 35438-done <at> debbugs.gnu.org
Subject: Re: Document IBM Z environment variables
Date: Sun, 5 Jan 2020 13:55:45 -0800

Re https://bugs.gnu.org/35438
Thank you. I've pushed that patch with a tiny wording change at the end.

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