packed_ref_cache: don't use mmap() for small files

kgybels · gitster · commit ba41a8b60087 · 2018-01-24T12:55:26.000-08:00
Take a hint from commit ea68b0c (hash-object: don't use mmap() for small files, 2010-02-21) and use read() instead of mmap() for small packed-refs files. Signed-off-by: Kim Gybels <kgybels@infogroep.be> Signed-off-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu> Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/refs/packed-backend.c b/refs/packed-backend.c
@@ -458,6 +458,8 @@ static void verify_buffer_safe(struct snapshot *snapshot)
 				 last_line, eof - last_line);
 }
 
+#define SMALL_FILE_SIZE (32*1024)
+
 /*
  * Depending on `mmap_strategy`, either mmap or read the contents of
  * the `packed-refs` file into the snapshot. Return 1 if the file
@@ -495,7 +497,7 @@ static int load_contents(struct snapshot *snapshot)
 
 	if (!size) {
 		return 0;
-	} else if (mmap_strategy == MMAP_NONE) {
+	} else if (mmap_strategy == MMAP_NONE || size <= SMALL_FILE_SIZE) {
 		snapshot->buf = xmalloc(size);
 		bytes_read = read_in_full(fd, snapshot->buf, size);
 		if (bytes_read < 0 || bytes_read != size)
