Re: Autoconf distributions and xz dependency

[Jim Meyering]

Eric Blake wrote:

> On 03/02/2012 10:24 AM, Jim Meyering wrote:
>> Bob Friesenhahn wrote:
>>
>>> On Fri, 2 Mar 2012, Bob Friesenhahn wrote:
>>>>
>>>> I tried to test how much peak memory 'xz' uses to decompress the
>>>> autoconf tarball but was (apparently) defeated by the strange way
>>>> that 'xz' is linked. I will try again with a different tool this
>>>> weekend.
>>>
>>> Ok, I have now measured how much memory the 'xz' I have here requires
>>> under Linux to decompress the autoconf beta tarball.  It requires
>>> 67,184,168 bytes of heap memory.  This seems to match the xz
>>> documentation for the -9 compression level.
>>
>> The autoconf tarball is not large enough to warrant using xz's -9 option.
>> A simple xz -e (i.e., use the default of -6) should be fine.
>
> What's the magic to add to cfg.mk to get that change in default?  I just
> used gnulib's maint.mk 'make beta' to make the 2.68b tarball, so if the
> defaults are wrong in maint.mk, maybe we should be fixing things
> upstream from autoconf.

It depends on the size of your tarball.
Since autoconf's is smaller than 8MiB, the default of -6 is perfect
and there is no benefit even from using -7.
Here's the gnulib patch that I'll soon push:

>From c60ba70014f8948154e1157fb2b5d4af88e5ebbc Mon Sep 17 00:00:00 2001
From: Jim Meyering <address@hidden>
Date: Fri, 2 Mar 2012 18:35:12 +0100
Subject: [PATCH] maint: don't specify XZ_OPT=-9ev in dist-related rule

Using xz's -9 option is warranted only if you have a very large
tarball (see xz's documentation for the sizes vs. presets), and
requires 64MiB of memory at decompression time.
* top/maint.mk (alpha beta stable): Don't specify XZ_OPT=-9ev.
Automake's default of just "-e" is fine.  Override on a
per-package basis by setting XZ_OPT e.g., in cfg.mk.
---
 ChangeLog    |   10 ++++++++++
 top/maint.mk |    2 +-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index c3490a0..ab73cce 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2012-03-02  Jim Meyering  <address@hidden>
+
+       maint: don't specify XZ_OPT=-9ev in dist-related rule
+       Using xz's -9 option is warranted only if you have a very large
+       tarball (see xz's documentation for the sizes vs. presets), and
+       requires 64MiB of memory at decompression time.
+       * top/maint.mk (alpha beta stable): Don't specify XZ_OPT=-9ev.
+       Automake's default of just "-e" is fine.  Override on a
+       per-package basis by setting XZ_OPT e.g., in cfg.mk.
+
 2012-03-01  Eric Blake  <address@hidden>

        maint.mk: allow announcement for non-gnulib project
diff --git a/top/maint.mk b/top/maint.mk
index 4cbd5f4..a97e0bd 100644
--- a/top/maint.mk
+++ b/top/maint.mk
@@ -1332,7 +1332,7 @@ alpha beta stable: $(local-check) writable-files 
$(submodule-checks)
        $(MAKE) vc-diff-check
        $(MAKE) news-check
        $(MAKE) distcheck
-       $(MAKE) dist XZ_OPT=-9ev
+       $(MAKE) dist
        $(MAKE) $(release-prep-hook) RELEASE_TYPE=$@
        $(MAKE) -s emit_upload_commands RELEASE_TYPE=$@

--
1.7.9.2.324.g1221