I wanted to profile the memory usage of a script. Here's the output before it was running:

procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
0  0  15624 186660  39460 439052    0    0     0     2    1    1  0  0 100  0

Here's the output while the script is running, at the point where free memory was at its lowest value:

procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu----
r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa
0  0  15624  11464  40312 473524    0    0     0     2    1    1  0  0 100  0

So free memory dropped by about 175 MB, and I expected that buff would increase by that amount. But it seems the other columns changed by relatively negligible amounts - how is this possible? Am I interpreting this wrong, or is some memory just not being accounted for in this output?