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The combination of direct application access to volatile memory combined with the
operating system I/O access to storage devices supports the most common application
programming model taught in introductory programming classes. In this model,
developers allocate data structures and operate on them at byte granularity in memory.
When the application wants to save data, it uses standard file API system calls to write
the data to an open file. Within the operating system, the file system executes this write
by performing one or more I/O operations to the storage device. Because these I/O
operations are usually much slower than CPU speeds, the operating system typically
suspends the application until the I/O completes.
Since persistent memory can be accessed directly by applications and can persist
data in place, it allows operating systems to support a new programming model that
combines the performance of memory while persisting data like a non-volatile storage
device. Fortunately for developers, while the first generation of persistent memory
was under development, Microsoft Windows and Linux designers, architects and
Figure 3-1. Storage and volatile memory in the operating system
Chapter 3 Operating SyStem SuppOrt fOr perSiStent memOry