Contrary to what you might read in many articles, the commit charge is not a measurement of anything that physically exists. Not physical memory, the pagefile, or any combination of the two. It can be considered the sum total of the RAM and pagefile needed to store the private virtual address space allocated by all running processes, if they actually used all they allocate. Most applications allocate more than they actually use. Memory for program code, DLL's etc. is not included in this total.
Windows keeps track of the commit charge to make sure that there is some place to store all of this potential data, just in case the running applications were to use all the space they have allocated. The commit limit is the size of RAM, minus some overhead, plus the size of the pagefile. Not all of RAM is available to the commit charge.
The important thing to remember about the commit charge is that it must always be below the commit limit. If it hits the limit bad things will happen, such as application or system failures. Since the commit charge doesn't represent anything physical it is of little importance to performance