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don't let the delta cache grow unbounded in 'git repack'

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I have 4GB of RAM on my system which should, in theory, be quite enough
to repack a 600 MB repository.  However the unbounded delta cache size
always pushes it into swap, at which point everything virtually comes to
a halt.  So unbounded caches are never a good idea.

A default of 256MB should be a good compromize between memory usage and
speed where medium sized repositories are still likely to fit in the
cache with a reasonable memory usage, and larger repositories are going
to take quite some time to repack already anyway.

While at it, clarify the associated config variable documentation
entries a bit.

Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Nicolas Pitre 2009-08-05 16:55:07 -04:00 committed by Junio C Hamano
parent f0df1293ac
commit 5749b0b2f9
2 changed files with 12 additions and 4 deletions
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14
Documentation/config.txt
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@ -1218,12 +1218,20 @@ pack.compression::
pack.deltaCacheSize::
The maximum memory in bytes used for caching deltas in
linkgit:git-pack-objects[1].
A value of 0 means no limit. Defaults to 0.
linkgit:git-pack-objects[1] before writing them out to a pack.
This cache is used to speed up the writing object phase by not
having to recompute the final delta result once the best match
for all objects is found. Repacking large repositories on machines
which are tight with memory might be badly impacted by this though,
especially if this cache pushes the system into swapping.
A value of 0 means no limit. The smallest size of 1 byte may be
used to virtually disable this cache. Defaults to 256 MiB.
pack.deltaCacheLimit::
The maximum size of a delta, that is cached in
linkgit:git-pack-objects[1]. Defaults to 1000.
linkgit:git-pack-objects[1]. This cache is used to speed up the
writing object phase by not having to recompute the final delta
result once the best match for all objects is found. Defaults to 1000.
pack.threads::
Specifies the number of threads to spawn when searching for best

2
builtin-pack-objects.c
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@ -86,7 +86,7 @@ static int pack_compression_level = Z_DEFAULT_COMPRESSION;
static int pack_compression_seen;
static unsigned long delta_cache_size = 0;
static unsigned long max_delta_cache_size = 0;
static unsigned long max_delta_cache_size = 256 * 1024 * 1024;
static unsigned long cache_max_small_delta_size = 1000;
static unsigned long window_memory_limit = 0;