CODEWITHSUNDEEP
c++ubuntumemorymemory-management
rahman
rahman

Reputation: 4948

Why my systems doesnt free the buffers/cache

I have a memory hungry application. I let it run over night on a system with 32GB RAM. Also ran free -m -s 20 along with it to see how the memory status changes. My application was the only thing I manually started after restarting my Ubuntu (except the terminal of course). let's look at parts of output:

when the application started:

             total       used       free     shared    buffers     cached
Mem:         32100       1428      30671         35         69        594
-/+ buffers/cache:        765      31335
Swap:        32693          0      32693

before the application ends:

             total       used       free     shared    buffers     cached
Mem:         32100      31860        240         84          2      17420
-/+ buffers/cache:      14437      17663
Swap:        32693         12      32681

right after the application ends:

             total       used       free     shared    buffers     cached
Mem:         32100      18723      13376         84          2      17434
-/+ buffers/cache:       1285      30814
Swap:        32693         12      32681

and the status remain same for many hours until I came back in the morning.

My question is: Why most of my memory is still considered a free part of buffers/cache ? when is this part of memory going to be the free part of the overall Mem: again?

I then opened a browser, an IDE and some other GUI application to see how and from where the memory is allocated to the new applications:

             total       used       free     shared    buffers     cached
Mem:         32100      20378      11721         88        160      18075
-/+ buffers/cache:       2143      29956
Swap:        32693         12      32681

Apparently, Free memory from both Mem: as well as buffers/cache: was allocated to new applications. Can you please interpret this for me?

Upvotes: 0

Views: 87

Answers (1)

user3985238
user3985238

Reputation:

The cached data is also part of the used memory. After a program ends, the data loaded from disk by your program will become a part of the cache. So your system will not free any of the data, but it drops the cached data, if your memory will be needed again. A more or less funny page, that describes the problem.

Upvotes: 2

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