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You are here: MacNN Forums > Software - Troubleshooting and Discussion > macOS > Memory- Wired, Active, Inactive, Free

Memory- Wired, Active, Inactive, Free
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adios
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May 26, 2005, 12:30 PM
 
Just curious about the categories that the Activity Monitor has for memory. I'm assuming that 'Wired' memory is used by the OS, 'Active' is used by the open apps, and 'Free' is completely unused memory. True? If so, then what is 'Inactive' memory?

Thanks, Andy
     
Louis_SX
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May 26, 2005, 12:36 PM
 
My guess is that "incative" memory is sytem cache, but I'm not 100% sure on that.
     
Catfish_Man
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May 26, 2005, 12:42 PM
 
Memory that's holding old stuff so that if you reopen it, it'll be faster. Ideally you'll have lots of inactive memory and very little free
     
adios  (op)
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May 26, 2005, 02:51 PM
 
When Activity Monitor is showing CPU performance, what does it mean by 'Nice?'
     
sodamnregistered2
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May 27, 2005, 03:05 AM
 
Originally Posted by adios
When Activity Monitor is showing CPU performance, what does it mean by 'Nice?'
Open the terminal and type "man nice"

nice -- execute a utility with an altered scheduling priority
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Chuckit
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May 27, 2005, 03:16 AM
 
I'm still not sure how a percentage of its CPU usage can be nice, though. It could mean it took that percentage from another application due (due to its nice level), it yielded that much to another application (due to its nice level) or something else entirely. It seems a little ambiguous to me, and I haven't found the Google terms to figure out which it is.
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andreadeca
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May 27, 2005, 06:09 AM
 
Here is an excerpt from http://www.desertsol.com/~kevin/free/

- - - - -
Summary of the terms "wired", "active", "inactive", "used", "free", excerpted from the link above:

Wired = memory allocated that shouldn't/can't be swapped/paged out (ie its locked into memory -- possibly portions of the OS code for example).

Active = allocated memory that has been accessed during last N seconds.

Inactive = allocated memory that hasn't been accessed during last N Secs (quite likely to be first candidates for being swapped/paged out if memory being demanded). [I always think of Inactive memory as the memory used by caches]

Used = Wired + Active + Inactive

Free = memory that isn't allocated to any process or the kernel.

- - - - - -

Andrea
     
eevyl
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May 27, 2005, 01:24 PM
 
Other nice definition of free memory for Mac OS X is "wasted memory". And it's true, indeed it is.
     
Millennium
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May 27, 2005, 02:10 PM
 
Wired memory contains code which can't be paged out to disk, no matter how recently it has been used. The most common code to be "wired" like this is the virtual-memory subsystem, because if you paged this out to disk you wouldn't be able to get it back into memory. Sometimes other portions of the OS will be put here, though. Memory which contains password information (such as storing the password which the user just typed in) should ideally be wired, so that it won't be written to disk if the system needs to page some things out.

Wired memory is necessary in some situations, so you're never going to get it down to zero. However, it does come at a price, because it means that less memory is available for paging in and out. In general, you don't want to have a lot of wired memory; only things that have to be wired should be.
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Strix
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May 27, 2005, 02:35 PM
 
With regards to Page Ins/Outs, what is a "good" level of paging in & out.

For example Activity Monitor currently tells me that I have 54449 Page Ins and 22140 Page Outs. Free Memory stands at 6.25MB. I have open five applications (Activity Monitor, Route 66, Safari, Mail and iTunes) which is quite typical.

My computer is an iBook 500Mhz with 384MB RAM and X 10.3.9
     
Detrius
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May 27, 2005, 03:22 PM
 
Originally Posted by Strix
With regards to Page Ins/Outs, what is a "good" level of paging in & out.

For example Activity Monitor currently tells me that I have 54449 Page Ins and 22140 Page Outs. Free Memory stands at 6.25MB. I have open five applications (Activity Monitor, Route 66, Safari, Mail and iTunes) which is quite typical.

My computer is an iBook 500Mhz with 384MB RAM and X 10.3.9
One page is 4kB, so how good or bad that is depends entirely on how long your machine has been on. 22k pages is less than 100MB. If your machine has been up for a half an hour, this is bad. If it's been running for a week, this is good. Ideally, you would have enough RAM that you would NEVER have pageouts. BTW, you can't avoid pageins, as these occur when you open an application. However, you will have MORE pageins as your pageouts increase.
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Millennium
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May 27, 2005, 03:23 PM
 
Ideally, you want as few pageins/pageouts as possible, but the important thing is not to have so many that your hard drive shows huge amounts of activity while things slow to a crawl. When this happens, the hard drive is said to be thrashing, and it's not a good situation to be in: not technically harmful, but very annoying.
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chabig
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Jun 19, 2005, 04:07 PM
 
     
   
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