[PATCH] don't let the delta cache grow unbounded in 'git repack'
From: Nicolas Pitre <hidden>
Date: 2016-06-15 22:47:09
Subsystem:
documentation, the rest · Maintainers:
Jonathan Corbet, Linus Torvalds
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 <redacted>
diff --git a/Documentation/config.txt b/Documentation/config.txt
index c6f09f8..7791c32 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt@@ -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
diff --git a/builtin-pack-objects.c b/builtin-pack-objects.c
index 961b639..c433748 100644
--- a/builtin-pack-objects.c
+++ b/builtin-pack-objects.c@@ -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;