> also vmstat's avm field is a
> little, uh, wrong too..

let me guess, it says something like:

 procs   memory     page                    disks         faults      cpu
 r b w   avm   fre  flt  re  pi  po  fr  sr ?0 ?1 ?2 ?3   in   sy  cs us sy id
 1 0 0 78668 12636   24   4   1   0   0   0  0  0  0  0    0  254  32 10  5 85

i.e. avm is much more than the amount of RAM in your machine?

well, you know...  from the man page for vmstat:

       memory Information  about  the  usage  of virtual and real
              memory.  Virtual pages (reported in units  of  1024
              bytes) are considered active if they belong to pro-
              cesses which are running or have run in the last 20
              seconds.

              avm  active virtual pages
              fre  size of the free list

now, you'll note that what that ends up saying is that all virtual
pages in all processes that have been run in the last 20 seconds are
counted...

which means that, say, if a process with N k of 'personal' use of RAM
also happens to mmap() in 1M of shared libraries, that 1M of virtual
memory will be added to AVM.  this is because even though the object
backing them might be the same, the fact that it's mapped 2x (or N
times) means that there are N _virtual_ copies...

So, that number is correct.

However, it's not very useful.  A more useful measure would be, for
instance, the amount of memory being used by active virtual memory in
the system...


I've heard of at least one patch to make this number 'more useful',
but i've not yet had time to investigate it.


cgd

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