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Memory on its limit

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Carlo Ferraro
Memory on its limit
on Jul 13, 2014 at 1:00:55 am

Got an Imac quad 3.4, 2GB graphics. Had 16GB Ram but it always got clogged with FCPX and Lightroom, so I raised it to 32GB. It got much better but today (disgracefully) updated to 10.9.4 and the problem is present again, no FCPX, no other program, 27GB of ram are on File Cache. Cleaned up with Cleanyourmac and manually searched on cache fils in the library files, there are none after CYmac. If I hit repeatedly clean memory on Memory Clean app it cleans about 1GB at a time but in the end the files cage absorbs 70-75% of the memory.
Getting mad at Apple!
Any hint?

Imac 27 Quad 3.4, 16GB Ram, 2GB Graphics, 6GB USB3.0 & Esata Raids
http://www.ferrarofilmsau.com


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Chris Gordon
Re: Memory on its limit
on Jul 13, 2014 at 5:24:06 pm

You don't have a problem if you're just seeing memory used by the file cache. In fact, you normally want file cache to be used. The file cache is the OS caching recently accessed files in memory. This is under the theory that the likelihood of a file being accessed is higher if it's already been accessed recently. Caching it in memory makes the subsequent access faster (read from memory instead of disk). Mac OS X, like pretty much every other UNIX flavor out there, will normally use all available memory for this cache. When memory is actually needed by a running program, it will automatically take that memory for the cache and purge some of the file cache. Any UNIX-like machine running for any non-trivial amount of time doing anything non-trivial work should have a sizable file cache. It is normally to see very little "free" memory since these cache's SHOULD take up the un-used memory since this can make things faster.

Now, how do you know if you really have a memory problem...

The way to know if you need memory is to see if you are using a lot of swap. If you have a lot of swap used, you probably need more memory for what you're trying to run. The even better way to know is if you see a lot of swapins and swapouts (from something like vm_stat -- a command line tool you run in Terminal). When there is real pressure on memory: the programs you are trying to run need more memory than your system has RAM, the OS will take some things in RAM and move them to disk (swap is sort of like a disk based RAM). When you need to access the program that has been swapped out to disk, it must first be read back into RAM (and probably something else swapped out to make room). In the worst case situation of your system being extremely memory starved, it spends a lot of time swapping things to disk and other things back to memory (thrashing). Obviously this will be excruciatingly slow. The number of "swapins" and "swapouts" shows the rate at which memory pages are moving back and forth. Normally this is 0. Something higher can indicate a need for more memory.

So to your specific case:
- Where you experiencing problems at 16 GB or was it just that you saw a large page cache? What were the problems?
- Are you experiencing problems at 32 GB now or just seeing a large page cache?
- The caches files in ~/Library are completely different than RAM caches and are unrelated to the amount of memory in your system.
- The file cache at 70%-75% of your RAM is a *GOOD* thing. You want this as it will make your system faster in general.
- If you want to purge the file cache, you can use the "purge" command from the command line. Open Terminal and type "sudo purge". This command is part of the OS and you don't need any special applications to run it.

Hope that helps, but I'm pretty sure you don't have any actual problems.


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Carlo Ferraro
Re: Memory on its limit
on Jul 13, 2014 at 6:26:12 pm

Well, I am happy to had gone to the forum.
Much appreciated you took the time for the explanation.

Imac 27 Quad 3.4, 16GB Ram, 2GB Graphics, 6GB USB3.0 & Esata Raids
http://www.ferrarofilmsau.com


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Carlo Ferraro
Re: Memory on its limit
on Jul 14, 2014 at 12:30:59 am

So to your specific case:
- Where you experiencing problems at 16 GB or was it just that you saw a large page cache? What were the problems?

Problems here were when using FCPX and Lightroom at the same time, I am aware that Adobe is a shark eating beast, as well as FCPX when rendering on the background

Are you experiencing problems at 32 GB now or just seeing a large page cache?
For now just seeing a big amount on cache files. When I have a session with LR and FCP will do the comparison

- The caches files in ~/Library are completely different than RAM caches and are unrelated to the amount of memory in your system.

OK copied that

- The file cache at 70%-75% of your RAM is a *GOOD* thing. You want this as it will make your system faster in general.

- If you want to purge the file cache, you can use the "purge" command from the command line. Open Terminal and type "sudo purge". This command is part of the OS and you don't need any special applications to run it.

Got it
Will follow your advise and let's see how it goes.
Thanks again

Imac 27 Quad 3.4, 16GB Ram, 2GB Graphics, 6GB USB3.0 & Esata Raids
http://www.ferrarofilmsau.com


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Chris Gordon
Re: Memory on its limit
on Jul 14, 2014 at 2:58:29 am

What were the problems you saw with 16GB?

Both LR and FCPX access a lot of big files. It's very reasonable to expect the file cache to be as big as possible when using these. In fact you generally want this as it helps speed things up a bit.

To monitor, just watch the Memory tab/section of Activity Monitor and see if Swap starts getting used.


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