off-topic -> memory usage

[Denys Vlasenko]

On Wednesday 02 February 2011 16:33, David Collier wrote:
> So the question is - how close is this box to the OOM of doom - is the
> inactive cached memory available for re-use if it's needed, or am I
> really 2M from the drop?

One tool is free:

$ free
             total         used         free       shared      buffers
Mem:       2054936      1078352       976584            0        94084
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ mostly irrelevant
-/+ buffers:             984268      1070668  <=== useful
Swap:       131068            0       131068


Another is nmeter:

$ nmeter '%t %c alloc:%m free:%[mf]'
03:45:35 .......... alloc:190m free:1.7g
03:45:36 .......... alloc:190m free:1.7g
03:45:37 .......... alloc:190m free:1.7g
^C

Second estimate (1.7g) looks to be more correct than what free
says (1g) (because our free doesn't analyze Cached:NNN line):

$ dd bs=1700M count=1 </dev/zero >/dev/null

wasn't swapping (I heard no disk seeking), whereas

$ dd bs=1800M count=1 </dev/zero >/dev/null

swapped about 100M according to free:

$ free
             total         used         free       shared      buffers
Mem:       2054936       225076      1829860            0         9252
-/+ buffers:             215824      1839112
Swap:       131068       121428         9640


-- 
vda