Re: git grep performance regression

From: Duy Nguyen <pclouds@gmail.com>
Date: Jan 15, 2013, 04:38 UTC
Message-ID: <CACsJy8AnABCisgSVL7Qh_-uejAJA3x1kzy=4i+uXm3+90m5tuA@mail.gmail.com>
In-Reply-To: <CACsJy8A7FLYqdY2Mt5pUq0nH3N8mbZ4crkYJYFfepp19c0aWhg@mail.gmail.com>

On Tue, Jan 15, 2013 at 9:46 AM, Duy Nguyen <pclouds@gmail.com> wrote:

> I don't have time to look into details now, but by enabling
> DEBUG_ATTR, it looks like this commit makes it push and pop patterns a
> lot more than without the commit.

I think the culprit is at this chunk:

 static void prepare_attr_stack(const char *path)
 {
        struct attr_stack *elem, *info;
        int dirlen, len;
        const char *cp;

-       cp = strrchr(path, '/');
-       if (!cp)
-               dirlen = 0;
-       else
-               dirlen = cp - path;
+       dirlen = find_basename(path) - path;

dirlen is not expected to include the trailing slash, but find_basename() does that. It messes up with the path filters for push/pop in the next code. This brings grep performance closely back to before for me. Ross, can you check (patch could be whitespace damaged by gmail)?

-- 8< --

diff --git a/attr.c b/attr.c
index b05110d..1e96e26 100644
--- a/attr.c
+++ b/attr.c
@@ -583,6 +583,9 @@ static void prepare_attr_stack(const char *path)

        dirlen = find_basename(path) - path;

+       if (dirlen)
+               dirlen--;
+
        /*
         * At the bottom of the attribute stack is the built-in
         * set of attribute definitions, followed by the contents
-- 8< --