[PATCH] Bump core.deltaBaseCacheLimit to 128MiB

From: David Kastrup <dak@gnu.org>
Date: Mar 19, 2014, 09:13 UTC
Message-ID: <1395220419-4541-1-git-send-email-dak@gnu.org>

The default of 16MiB causes serious thrashing for large delta chains combined with large files. --- 128MiB seems like a big bump, but the limit for files not getting delta compressed at all is 512MiB and it would appear that they should be a bit comparable. It is hard to find good benchmarks here: basically the best benchmark I found was git blame with problematically large repositories compressed with the (old) git-gc --aggressive settings, using not-yet-committed but presented code (the current blame code spends so much time thrashing in other places that the benchmark differences are less obvious).

Documentation/config.txt | 2 +-
 environment.c            | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 73c8973..1b6950a 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -484,7 +484,7 @@ core.deltaBaseCacheLimit::
 	to avoid unpacking and decompressing frequently used base
 	objects multiple times.
 +
-Default is 16 MiB on all platforms.  This should be reasonable
+Default is 128 MiB on all platforms.  This should be reasonable
 for all users/operating systems, except on the largest projects.
 You probably do not need to adjust this value.
 +
diff --git a/environment.c b/environment.c
index c3c8606..73ed670 100644
--- a/environment.c
+++ b/environment.c
@@ -37,7 +37,7 @@ int core_compression_seen;
 int fsync_object_files;
 size_t packed_git_window_size = DEFAULT_PACKED_GIT_WINDOW_SIZE;
 size_t packed_git_limit = DEFAULT_PACKED_GIT_LIMIT;
-size_t delta_base_cache_limit = 16 * 1024 * 1024;
+size_t delta_base_cache_limit = 128 * 1024 * 1024;
 unsigned long big_file_threshold = 512 * 1024 * 1024;
 const char *pager_program;
 int pager_use_color = 1;

-- 
1.8.3.2