d.

Before patch:
$ dd if=/dev/sda of=/dev/null bs=2M count=64 iflag=direct
134217728 bytes (134 MB) copied, 5.29612 s, 25.3 MB/s

After patch:
$ dd if=/dev/sda of=/dev/null bs=2M count=64 iflag=direct
134217728 bytes (134 MB) copied, 3.94955 s, 34.0 MB/s

Signed-off-by: Dan McGee <dpmcgee@gmail.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>