Memory Statistics
Virtual memory & performance
When MacOS X runs out of memory, it uses a portion of your harddisk as an extension of it's physical RAM. It does so by moving the contents of less frequently used chunks of RAM to disk, making room for new programs or data. When this chunk is needed again, it is moved back to RAM. The process of moving stuff in and out of RAM is called paging , because the size of such a chunk of RAM is called a page.Because the memory created by this technique doesn't really exist, it is called virtual memory (VM). Virtual memory ensures you will almost never run out of memory. So where's the catch? Accessing a page on disk is many times slower than acessing RAM, so too much paging can slow your Mac down to a crawl. Therefore you should have enough RAM to ensure that you don't get too much paging.
Do I have enough RAM ?
Keep-It-Up-X will collect statistics about how much paging is going on while you're using your Mac. These statistics can help you determine if you have enough RAM or not.1. Acessing the memory statistics
- launch KIU to start collecting statistics
- Use your Mac as usual for about an hour.
- You can use a webbrowser to access the KIU Web Interface and get the statistics for the past hour:
- select the Memory Statistics menu
- you now have the option of getting statistics with a 1 or 5 minute interval. The 1 minute intervals will give you a more accurate reading. The 5 minute intervals give a more condensed report but peak values will be averaged out.
- You'll get a table which will give you the statistics for the past hour and will typically look something like this:
| Time | pageins/s | pageouts/s |
| 15:44 | 17 | 0 |
| 15:43 | 14 | 7 |
| 15:42 | 1 | 4 |
- pageins/s: number of pages paged from disk to RAM per second (=paging rate in)
- pageouts/s: number of pages paged from RAM to disk per second (=paging rate out)
2. Interpreting the memory statistics
The values you get in the memory statistics table are color coded. You should look which colors dominate the table to determine what to do. E.g. if you get mostly greens and only a few reds, there's probably no need to add more RAM. If you get lots of reds, you should probably add more RAM.Ratings for the 1-minute interval statistics
|
Paging rate
|
color code
|
Rating
|
Recommendation
|
|
0 - 5
|
green
|
low
|
probably no need to add RAM
|
|
6 - 10
|
orange
|
moderate
|
consider adding some RAM for a moderate speed increase
|
|
11-20
|
red
|
high
|
adding RAM will significantly speed up your Mac
|
|
larger than 20
|
purple
|
extermely high
|
adding lots of RAM is absolutely necessary to get
a major speed increase
|
Ratings for the 5-minute interval statistics
|
Paging rate
|
color code
|
Rating
|
Recommendation
|
|
0 - 4
|
green
|
low
|
probably no need to add RAM
|
|
5 - 9
|
orange
|
moderate
|
consider adding some RAM for a moderate speed increase
|
|
10-15
|
red
|
high
|
adding RAM will significantly speed up your Mac
|
|
larger than 15
|
purple
|
extermely high
|
adding lots of RAM is absolutely necessary to get
a major speed increase
|
Note:
Even if there's little or no paging going on in your Mac, some types of applications may still benefit from adding extra RAM, because these applications might allocate larger caches or buffers.
Disclaimer:
The VM statitics are only a tool to help you determine why your Mac may be slow. Besides a lack of memory, there are lots of other reasons why performance may be inadequate. The author of KIU does not guarantee that adding RAM will solve all performance problems.