diesel said:
I'm confused as to what the PF usage box and graph shows. The Microsoft docs
say they show how the pagefile is being used. Well, I have 1gb RAM and with
nothing really running the usage screen shows:
PF Usage shows 192mb
Physical Memory:
Total 1048092
Available 797952
System Cache 131356
There is plenty of physical memory available why is the Pagefile being used?
Shouldn't "PF Usage" show 0mb until I run out of physical memory?
Thanks.
There are two kinds of page file usage.
The first is actual usage, which means the actual movement of active
memory content from RAM to the page file so as to allow that RAM to be
used for other, currently more important, tasks. This is what the
utility that Gerry Cornell referred you to reports.
The second kind is, for want of a better term, "virtual" page file
usage. This is what Task Manager reports on the Performance tab. This
virtual usage of the page file includes not just the actual usage (if
any) but also the usage of the page file address space by Windows to
satisfy the unused portion of Memory Allocation Requests.
This is sometimes a bit difficult to grasp. What happens is that
application programs, device drivers, and Windows components typically
request memory allocations that are larger than what they actually
need under normal circumstances. There are sound reasons for doing
this, or so I am assured by experienced programmers. Windows must, by
definition, identify memory locations for all requested memory. So
what happens is that the Windows memory manager allocates addresses in
RAM only to those portions of these requests that are actually used.
The unused portions are allocated memory address space in the page
file. Note that this allocation of page file addresses does not
involve any actual disk activity - just entries in the memory mapping
tables maintained by the CPU.
And if it subsequently happens that a program needs to use a
previously unused portion of the memory it requested then the memory
manager will instantaneously remap that portion to available locations
in RAM.
Here are some current figures from my own computer:
- Actual page usage = 47 mb
- Current page file size = 160 mb
(these two values are from Bill James' utility)
- Page file usage = 333 mb
(from Task Manager)
Note that Task Manager is reporting a figure that exceeds the actual
current size of the page file. This is okay in Windows XP, so long as
the Task Manager value does not exceed the maximum size limit for the
page file because the page file could be increased in size should that
become necessary, again provided that there is enough free space on
the hard drive to do so.
Note also the difference between the Task Manager figure of 333 mb and
the Actual usage figure of 47 mb. That figure, 286 mb at the moment,
represents the sum total of the unused portions of the memory
allocation requests that have been issued by everything that is
currently active on my machine.
Hope this clarifies the situation.
Good luck
Ron Martell Duncan B.C. Canada
--
Microsoft MVP
On-Line Help Computer Service
http://onlinehelp.bc.ca
"The reason computer chips are so small is computers don't eat much."
