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Discussion in 'macOS' started by sukanas, Nov 8, 2008.
how does it work? and does it 'really work'?
There's no reason to free memory. Memory not in active use by software will become inactive memory, which is treated almost the same as free memory, but is used more quickly when opening applications that are still stored in inactive memory.
Simple terms: don't bother.
Yes. It works.
Works for me. Don't know what it does, but it definitely frees up memory.
I understand the theory of inactive memory, BUT in practice, single applications that use large amounts of RAM (like image processing or video editing apps) suffer because inactive memory is (i suspect) optimised for many small programs to be running simultaneously. The unix heritage is very good at that. Server's run lots of applications and there's lots of common code.
For a specific example, I have a macbook pro with 2gb ram. I'm stitching some images together with "Hugin", and the process "enblend" is using about 1GB of virtual ram, typically between 400mb and 850mb real ram depending on the part of its processing.
There's over 500mb inactive ram and 10mb free ram. enblend is using about 1% cpu because it's spending all it's time waiting for virtual memory.
All other apps have pretty much also ground to a halt as they have been paged out to disk.
So why is it that the mac memory manager doesn't clear out this inactive memory? I suspect that there is some internal threshold that doesn't like to have a single process using more than 50% of available ram, and so it won't clear the inactive memory for it. But... it's also used all of the free ram, so other apps are being pages out and slow down.
The cpu is sitting there doing nothing whilst the hard drive is getting completely thrashed.
Then, i downloaded iFreeMemory and let it do it's thing. Then there was 400MB free memory; still some inactive, but a lot less.
And now enblend is running at about 80% cpu, and can do this stitching in an hour instead of a day.
And the rest of the computer is now usable.
So....... Yes. It works.
^^ Yeah, what that guy said!
I use it, I use it on my Macbook Pro, as well as on my girlfriends clamshell. It definitely helps to hit "Optimize Memory" and sit back for a minute while it frees up inactive memory.
Perhaps it's more noticeable on machines with 2gb or less RAM, but my machine with 4gb gains pretty much no performance "freeing" memory before performing video transcoding. It could be due to the fact that MacBook Pros use slower drives, therefor you can feel paging out more.
You do what you gotta do, I suppose.
You can use Terminal's purge utility to free up inactive RAM. Just enter "purge" into the Terminal and hit enter.
Thanks for that command. I've had problems with Leopard not freeing up inactive RAM. I can definitely see this being useful.
I tried purge command in terminal and I got the following:
-bash: purge: command not found