test_root reorder(Re: [patch] ext2: Apply Jack's ext3 speedups)

[Prasanna Meda <pmeda@akamai.com>]

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Prasanna Meda wrote:

>   - Folded all three root checkings for 3,  5 and 7 into one loop.
>   -  Short cut the loop with 3**n < 5 **n < 7**n logic.
>   -  Even numbers can be ruled out.

Without going to that complicated path, the better performance
is achieved with just reordering  of the tests from 3,5,7 to 7,5.3, so
that average case becomes better. This is more simpler than
 folding  patch.


Thanks,
Prasanna.


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 Reorder test_root testing from 3,5,7 to 7,5,3 so
 that average case becomes good. Even number check
 is added. 

 Signed-off-by: Prasanna Meda <pmeda@akamai.com>

--- a/fs/ext3/balloc.c	Fri Jan 28 22:21:45 2005
+++ b/fs/ext3/balloc.c	Sat Jan 29 02:51:39 2005
@@ -1451,8 +1451,10 @@
 {
 	if (group <= 1)
 		return 1;
-	return (test_root(group, 3) || test_root(group, 5) ||
-		test_root(group, 7));
+	if (!(group & 1))
+		return 0;
+	return (test_root(group, 7) || test_root(group, 5) ||
+		test_root(group, 3));
 }
 
 /**