The truth about Virtual or Swap Memory
A lot has been said about how virtual memory increases system performance.
After RAM, people often suggest the second best way to get a speed boost is
to increase the size of pagefile.sys. Its time for debunking some myths
about virtual memory.
Here are a few false beliefs about virtual memory
More is better.
Setting a static swap file size will make virtual memory more effective.
Emptying the Pagefile will increase system performance.
All of these are false!!!!
What is virtual memory?
Without turning this into a lecture on Operating Systems, Ill explain what
Virtual memory is all about and keep it brief. Virtual memory is a
technique which gives an application program the impression that it has
contiguous working memory, while in fact it may be physically fragmented
and may even overflow on to disk storage.
Now, lets say I have 512MB RAM and running Adobe Photoshop and Firefox
simultaneously. On wndows XP, assuming 200MB is already allocated to the
kernal, the user applications i.e Photoshop and Firefox are left with 300
MB of space. Firefox will run smoothly while youll notice lag while working
with photoshop.
This is due to pagefaults which occur when the required amount of RAM is
insufficient and data needs to be fetched from the hard disk. Firefox can
accomodate itself well within 300MB of RAM but for photoshop it isnt a
sweet deal. Thats where virtual memory kicks in, the OS reserves some
portion of the hard disk as memory, hence the name virtual. As HDD space is
higher than RAM, programs use virtual address ranges which in total exceed
the amount of real memory.
Problem with virtual memory
As the memory available for the system increases, youd expect the
performance to increase. To a certain extent it does help but as read/write
speeds of electromagnetic HDD are very slow compared to the semiconductor
based RAM, it doesnt help even page file increases twice the size of your
main memory. Simply put, having over 1.5 GB of pagefile for 512 MB RAM is
not benefitial.
Now adays, RAM has become very inexpensive and 4GB RAM in dual channel is
very common. I prefer to disable page file as it saves me unnecessary read
writes cycles on the HDD while also conserving my laptop battery. 4GB of
memory is enough for most people and disabling the page file has given be
better results. It even has long term benefits as it prevents undue HDD
activity and increases its life.
Best way to enable virtual memory
If you do not plan to upgrade to 4GB memory, then you can still make the
best of your page file, by keeping it in a separate Hard drive altogether,
the read write headers are spared of the extra overhead as pagefaults are
dealt with in the other hard drive.
Never, keep the pagefile in a different partition than that of Windows in
the same HDD. Meaning, if you have only one hard disk then you should keep
the pagefile in the same partition as that of Windows and not a different
partition of the same hard drive as many people believe. As, doing so
results in the read/write heads requiring to travel large distances
spanning partitions back and forth!
