sha1_file.c: Round the mmap offset to half the window size.

This ensures that a given area is mapped at most twice, and greatly
reduces the virtual address space usage.

Signed-off-by: Alexandre Julliard <julliard@winehq.org>
Acked-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/sha1_file.c b/sha1_file.c
index 8ad7fad825708b5a56a3bfd4b8b98708de0bb2dc..b83f59f38320b349fa873f0505e74ae2ba75a99b 100644 (file)
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -407,7 +407,6 @@ static unsigned int peak_pack_open_windows;
 static unsigned int pack_open_windows;
 static size_t peak_pack_mapped;
 static size_t pack_mapped;
-static size_t page_size;
 struct packed_git *packed_git;
 
 void pack_report()
@@ -416,7 +415,7 @@ void pack_report()
                "pack_report: getpagesize()            = %10" SZ_FMT "\n"
                "pack_report: core.packedGitWindowSize = %10" SZ_FMT "\n"
                "pack_report: core.packedGitLimit      = %10" SZ_FMT "\n",
-               page_size,
+               (size_t) getpagesize(),
                packed_git_window_size,
                packed_git_limit);
        fprintf(stderr,
@@ -662,10 +661,9 @@ unsigned char* use_pack(struct packed_git *p,
                                break;
                }
                if (!win) {
-                       if (!page_size)
-                               page_size = getpagesize();
+                       size_t window_align = packed_git_window_size / 2;
                        win = xcalloc(1, sizeof(*win));
-                       win->offset = (offset / page_size) * page_size;
+                       win->offset = (offset / window_align) * window_align;
                        win->len = p->pack_size - win->offset;
                        if (win->len > packed_git_window_size)
                                win->len = packed_git_window_size;