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 32m: real 3m1.319s user 2m8.660s sys 0m51.904s 64m: real 2m20.636s user 1m55.780s sys 0m23.964s 96m: real 2m5.668s user 1m50.784s sys 0m14.288s 128m: real 2m4.337s user 1m50.764s sys 0m12.832s 192m: real 2m3.567s user 1m49.508s sys 0m13.312s Signed-off-by: David Kastrup <d...@gnu.org> --- 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; -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html