The pagefile provides two major benefits to the OS, neither of which is significantly influenced by a 64 bit OS.
- The pagefile increases the commit limit.
When an application allocates memory a Windows OS promises or commits itself to have available sufficient storage for it, even under a worst case scenario. This storage may be in RAM or the pagefile. The commit limit is defined as RAM size plus pagefile size minus a small overhead. With no pagefile the commit limit will be somewhat less than RAM size. The memory manager keeps track of the total allocated memory to ensure that this never exceeds the commit limit.
With no pagefile the commit limit is a hard limit that cannot be increased while the OS is running. With the default pagefile configuration the commit limit is not only much larger but it is a soft limit that can be increased by expanding the pagefile when this is necessary.
Hitting the commit limit in Windows is a bad thing. Most applications don't deal with this eventuality very well and the OS itself often cannot tolerate it.
- The pagefile optimizes RAM usage.
At any given time a computer is likely to contain a great deal of data that has not been accessed for a long time and in fact may never be accessed during the session. The memory manager of course has no way of knowing how important this data is so it must keep it somewhere.
Storing all this rarely used data in high speed RAM is a serious misuse of this precious resource. If RAM did not have this burden there would be more available for application use and for caching purposes. Caching is a really big deal in a modern OS and is a major contributor to good performance.
The pagefile provides a place where the memory manager can offload this rarely used data and relieving RAM from this duty. It is true there will be a cost in doing this but remember it is rarely used data so it should not be serious. And the memory manager has numerous optimizations to minimize this cost.
But rather than thinking of this as a cost, consider it an investment in performance. Just as making wise investments with money is a good thing, the memory manager invests a little time in using the pagefile in the anticipation that it will bring big dividends later. It usually works.
This is not some new idea. It has been used in Windows and Linux for many years and in large computer systems long before that. It is a tried and true principle that has been optimized over the decades.
Bottom line, let Windows manage the pagefile as it wishes. The designers know what they are doing. Unfortunately Microsoft has not done a very good job of communicating this to users and there are many misconceptions. A great deal of what you read on the Internet about the pagefile at the least contains serious errors.