Merge branch 'ea/blame-use-oideq'

[thirdparty/git.git] / builtin / index-pack.c

diff --git a/builtin/index-pack.c b/builtin/index-pack.c
index f865666db9ee62ba0b1dd60111912b233df47d7c..9721bf1ffe8eafad1d002203541d6a9d30a91f8e 100644 (file)
--- a/builtin/index-pack.c
+++ b/builtin/index-pack.c
@@ -1798,9 +1798,22 @@ int cmd_index_pack(int argc, const char **argv, const char *prefix)
 
        if (HAVE_THREADS && !nr_threads) {
                nr_threads = online_cpus();
-               /* An experiment showed that more threads does not mean faster */
-               if (nr_threads > 3)
-                       nr_threads = 3;
+               /*
+                * Experiments show that going above 20 threads doesn't help,
+                * no matter how many cores you have. Below that, we tend to
+                * max at half the number of online_cpus(), presumably because
+                * half of those are hyperthreads rather than full cores. We'll
+                * never reduce the level below "3", though, to match a
+                * historical value that nobody complained about.
+                */
+               if (nr_threads < 4)
+                       ; /* too few cores to consider capping */
+               else if (nr_threads < 6)
+                       nr_threads = 3; /* historic cap */
+               else if (nr_threads < 40)
+                       nr_threads /= 2;
+               else
+                       nr_threads = 20; /* hard cap */
        }
 
        curr_pack = open_pack_file(pack_name);