memory utilization questions

[David Wolfskill]

On Wed, Aug 06, 2014 at 02:53:14PM +0300, Stefan Parvu wrote:
> 
> Im planning to calculate real used, free memory. Can anyone confirm if these
> are correct:
> 
> 1. real used memory
> 
>  usedmem = totalmem - freemem,
> 
>     totalmem = vm.stats.vm.v_page_count x page_size
>     freemem = vm.stats.vm.v_free_count x page_size
> 
> 
>  2. real free memory
> 
>     realfree = inactive + cache + free ?
> 
>     inactive = vm.stats.vm.v_inactive_count x page_size
>     cache = vm.stats.vm.v_cache_count x page_size
>     free = vm.stats.vm.v_free_count x page_size
> ...

In what I have:

* I assume(!) that page size is invariant during any interval I care
  about.

* I do the calulations in KB (1024B), so I get the hw.pagesize OID &
  integer-divide that by 1024 to get a page_to_kb factor (e.g., for 4K
  pagesize, the factor is 4).

* Other OIDs: vm.stats.vm.v_active_count, vm.stats.vm.v_inactive_count,
  vm.stats.vm.v_wire_count, vm.stats.vm.v_cache_count,
  vm.stats.vm.v_free_count; I multiply each of these by the "page_to_kb
  factor" determined above (to get results in KB).

* Another OID: vfs.bufspace; I integer-divide this by 1024 (to get
  results in KB), as it seems to be in bytes vs. pages.

* Correspondence between names as used by top(1) vs. OID:
  Active: vm.stats.vm.v_active_count
  Inact:  vm.stats.vm.v_inactive_count
  Wired:  vm.stats.vm.v_wire_count
  Cache:  vm.stats.vm.v_cache_count
  Buf:    vfs.bufspace
  Free:   vm.stats.vm.v_free_count

Peace,
david
-- 
David H. Wolfskill				david at catwhisker.org
Taliban: Evil cowards with guns afraid of truth from a 14-year old girl.

See http://www.catwhisker.org/~david/publickey.gpg for my public key.
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