Beginning with SQL Server 2008 R2, log manager uses locked pages whenever possible for log cache buffers. This improves performance because the kernel of the OS doesn't need to lock these buffers during IO. The improvement effects may vary depending on many factors, but this change alone showed improvements around 1% in the results of a TPC-C run in low-end machines.
If something you want to take away from this post is that if you want your log manager to be able to perform somewhat more efficiently you need to grant Locked Pages in Memory privilege to the SQL service account and must be using the Enterprise Edition (or a Developer Edition or an Evaluation Edition, both of which behave exactly like the Enterprise does. The only difference among them three is their licensing.)
This post is part of the a series I decided to call “Understanding the value of the Enterprise Edition, one feature at a time” which I started in September 2011 and will grow on a weekly basis, having a new post incorporated to the family every Friday.