Turn off readahead on main mmap

It's harmful when the DB is larger than RAM.

diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index 058c68b..c086bd9 100644 (file)
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -2870,6 +2870,8 @@ mdb_env_open2(MDB_env *env)
                env->me_map = NULL;
                return ErrCode();
        }
+       /* Turn off readahead. It's harmful when the DB is larger than RAM. */
+       posix_madvise(env->me_map, env->me_mapsize, POSIX_MADV_RANDOM);
 #endif
 
        if (newenv) {