The default of 16m causes serious thrashing for large delta chains
combined with large files.

Here are some benchmarks (pu variant of git blame):

time git blame -C src/xdisp.c >/dev/null

for a repository of Emacs repacked with git gc --aggressive (v1.9,
resulting in a window size of 250) located on an SSD drive.  The file in
question has about 30000 lines, 1Mb of size, and a history with about
2500 commits.

16m (previous default):
real    3m33.936s
user    2m15.396s
sys     1m17.352s

real    3m1.319s
user    2m8.660s
sys     0m51.904s

real    2m20.636s
user    1m55.780s
sys     0m23.964s

real    2m5.668s
user    1m50.784s
sys     0m14.288s

real    2m4.337s
user    1m50.764s
sys     0m12.832s

real    2m3.567s
user    1m49.508s
sys     0m13.312s

Signed-off-by: David Kastrup <>
 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 1932e9b..21a3c86 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -489,7 +489,7 @@ 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 96 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 5c4815d..37354c8 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 = 96 * 1024 * 1024;
 unsigned long big_file_threshold = 512 * 1024 * 1024;
 const char *pager_program;
 int pager_use_color = 1;

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