vfs: drop conditional inode prefetch in __do_lookup_rcu
Linus Torvalds [Thu, 21 Jul 2011 18:01:42 +0000 (11:01 -0700)]
It seems to hurt performance in real life.  Yes, the inode will be used
later, but the conditional doesn't seem to predict all that well
(negative dentries are not uncommon) and it looks like the cost of
prefetching is simply higher than depending on the cache doing the right
thing.

As usual.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/dcache.c

index 6e4ea6d..fbdcbca 100644 (file)
@@ -1813,8 +1813,6 @@ seqretry:
                tname = dentry->d_name.name;
                i = dentry->d_inode;
                prefetch(tname);
-               if (i)
-                       prefetch(i);
                /*
                 * This seqcount check is required to ensure name and
                 * len are loaded atomically, so as not to walk off the