vfs: drop conditional inode prefetch in __do_lookup_rcu

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>

diff --git a/fs/dcache.c b/fs/dcache.c
index 6e4ea6d87774b6b31a212309fde5c3bed55a30c3..fbdcbca40725ab483f9b238c561c6dfb240db0bf 100644 (file)
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -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