comment on

I try to rearrange the expression to make it more clear:

A = B + C = G + H
G = B - E - F
H = C + E + F
[download]

It seems that:

Mem: 1034332 983572 50760 0 149028 530132
shows "buffers" and "cached" as part of "used" memory.

But -/+ buffers/cache: 304412 729920
shows "buffers" and "cached" as part of "free" memory

The -/+ buffers/cache line shows how much memory is used and free from the perspective of the applications.
--- from http://gentoo-wiki.com/FAQ_Linux_Memory_Management#The_difference_between_buffers_and_cache

And I do a test on my box, it shows that when the "free" memory is going to be exhausted, the kernel will take back all the "buffers" memory, but still left some "cached"memory. Following is the output by "free -m -s 1" when I increasingly created threads to consume the memory:

             total       used       free     shared    buffers     cac
+hed
Mem:          7973         68       7904          0          8        
+ 27
-/+ buffers/cache:         33       7939
Swap:         2047          0       2047

             total       used       free     shared    buffers     cac
+hed
Mem:          7973        106       7866          0          8        
+ 27
-/+ buffers/cache:         71       7902
Swap:         2047          0       2047
[download]

             total       used       free     shared    buffers     cac
+hed
Mem:          7973        112       7860          0          8        
+ 27
-/+ buffers/cache:         77       7896
Swap:         2047          0       2047

... ...

             total       used       free     shared    buffers     cac
+hed
Mem:          7973       7750        222          0          8        
+ 27
-/+ buffers/cache:       7714        258
Swap:         2047          0       2047

             total       used       free     shared    buffers     cac
+hed
Mem:          7973       7752        220          0          8        
+ 27
-/+ buffers/cache:       7716        256
Swap:         2047          0       2047

             total       used       free     shared    buffers     cac
+hed
Mem:          7973       7834        138          0          8        
+ 27
-/+ buffers/cache:       7798        174
Swap:         2047          0       2047

             total       used       free     shared    buffers     cac
+hed
Mem:          7973       7932         40          0          7        
+ 22
-/+ buffers/cache:       7903         69
Swap:         2047          0       2047

             total       used       free     shared    buffers     cac
+hed
Mem:          7973       7930         42          0          0        
+ 11
-/+ buffers/cache:       7917         55
Swap:         2047          2       2045

             total       used       free     shared    buffers     cac
+hed
Mem:          7973       7931         41          0          0        
+  3
-/+ buffers/cache:       7927         45
Swap:         2047        131       1915

             total       used       free     shared    buffers     cac
+hed
Mem:          7973       7925         47          0          0        
+  4
-/+ buffers/cache:       7920         52
Swap:         2047        144       1903

             total       used       free     shared    buffers     cac
+hed
Mem:          7973       7925         47          0          0        
+  4
-/+ buffers/cache:       7920         53
Swap:         2047        144       1903

             total       used       free     shared    buffers     cac
+hed
Mem:          7973       7925         47          0          0        
+  4
-/+ buffers/cache:       7920         53
Swap:         2047        144       1903
[download]

In reply to Re^2: [OT]What is "buffers" and "cached" memory in Linux system box? by sunshine_august
in thread [OT]What is "buffers" and "cached" memory in Linux system box? by sunshine_august

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