PDC 2009 Pre-Conference: Windows 7 Memory Management

At his lecture at the PDC’sWindows 7 Developer Boot Camp”, Landy Wang showcased many of the memory management changes done in Windows 7 and Windows Server 2008 R2 kernel, one of which is highlighted below. These changes, on average, lead to performance increase of up to two times in memory constrained systems – for free. All you have to do is move to the new operating system.

Removing the PFN Lock

The Page Frame Number (PFN) lock, up to Windows Vista (including), is a single lock in charge of almost all operations regarding page allocations in Windows memory, and as such it is a huge bottleneck when it comes to memory intensive applications and systems. For example, on a machine with 128 cores, SQL server reaches 88% contention over this lock, meaning that almost every second operation is stalled and takes precious time.

This lock has been removed and replaced with finer-grained locks on an individual memory page basis, achieving an up to x15 performance increase on a 32 processor machine. Note that this improvement comes for free to the developer who only needs to swap to the new OS.

Enjoy!

Comments are closed, but trackbacks and pingbacks are open.