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Old 04-06-2003, 07:45 PM   #1
piglingz
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Physical memory usage


HI, I'm running RedHat8 with P3 450MHz, and 312mb sd-Ram. Aftre initial boot, i check the mem stat with free, and it outputs about 80mb used - 220 mb free. When I transfer files via ftp to it, the mem usage grows. After transfering 100mb files, mem usage grows to 250mb used and 50mb free. Any Idea why the ftp transfer eats up so much mem and doesn't free it afterwards?
 
Old 04-06-2003, 08:30 PM   #2
jailbait
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disk cache

Linux is using memory for disk cache buffers.
 
Old 04-06-2003, 08:53 PM   #3
piglingz
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Any time this cached mem will free up? Thanks for your input.
 
Old 04-06-2003, 09:07 PM   #4
jailbait
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freeing cache memory

Linux keeps cache buffers as long as it can. If you happen to read that block again the cache will save you a disk read. Cache will expand until almost all memory is allocated. Then when something needs memory Linux will just give it the oldest cache buffers. Linux does something similar with previously use programs. It saves them in memory in case you want to run them again. So after you have run for a while all of memory appears used. You do not run into problems unless something needs memory and Linux does not have anything in memory that can be thrown away. Then instead of throwing away enough trash to accomodate the new request Linux saves some of the old memory allocations onto the swap file. If you start swapping everything runs slooooooooooooooooow.

So running with a high % memory allocation is normal. You have memory problems only if you start swapping.
 
  


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