[PATCH] Improve git-rev-list memory usage further

This avoids keeping tree entries around, and free's them as it traverses
the list. This avoids building up a huge memory footprint just for these
small but very common allocations.

Before:

	$ /usr/bin/time git-rev-list --objects v2.6.12..HEAD | wc -l
	11.65user 0.38system 0:12.65elapsed 95%CPU (0avgtext+0avgdata 0maxresident)k
	0inputs+0outputs (0major+42934minor)pagefaults 0swaps
	59124

After:

	$ /usr/bin/time git-rev-list --objects v2.6.12..HEAD | wc -l
	12.28user 0.29system 0:12.57elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
	0inputs+0outputs (0major+26718minor)pagefaults 0swaps
	59124

Note how the minor fault numbers - which ends up being how many pages we
needed to map - go down from 42934 (167 MB) to 26718 (104 MB).  That is:

Before:
	42934 minor pagefaults

After:

	26718 minor pagefaults

This is all in _addition_ to the previous fixes.  It used to be
~48,000 pagefaults.

That's still a honking big memory footprint, but it's about half of what
it was just a day or two ago (and this is the object list for a pretty big
update - almost 60,000 objects. Smaller updates need less memory).

Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/rev-list.c b/rev-list.c
index c410bc3..91534dd 100644 (file)
--- a/rev-list.c
+++ b/rev-list.c
@@ -147,11 +147,16 @@ static struct object_list **process_tree(struct tree *tree, struct object_list *
                die("bad tree object %s", sha1_to_hex(obj->sha1));
        obj->flags |= SEEN;
        p = add_object(obj, p, name);
-       for (entry = tree->entries ; entry ; entry = entry->next) {
+       entry = tree->entries;
+       tree->entries = NULL;
+       while (entry) {
+               struct tree_entry_list *next = entry->next;
                if (entry->directory)
                        p = process_tree(entry->item.tree, p, entry->name);
                else
                        p = process_blob(entry->item.blob, p, entry->name);
+               free(entry);
+               entry = next;
        }
        return p;
 }
@@ -218,12 +223,15 @@ static void mark_tree_uninteresting(struct tree *tree)
        if (parse_tree(tree) < 0)
                die("bad tree %s", sha1_to_hex(obj->sha1));
        entry = tree->entries;
+       tree->entries = NULL;
        while (entry) {
+               struct tree_entry_list *next = entry->next;
                if (entry->directory)
                        mark_tree_uninteresting(entry->item.tree);
                else
                        mark_blob_uninteresting(entry->item.blob);
-               entry = entry->next;
+               free(entry);
+               entry = next;
        }
 }