[erlang-questions] Memory Usage w/disc_copies

mats cronqvist <>
Thu Feb 19 08:34:20 CET 2009


"Kevin A. Smith" <> writes:

> I know this has been discussed on the list before but I haven't found  
> a satisfactory answer either in the list archives or Google.
>
> I've got some test code which queries 9 disc_copies tables in a tight  
> loop. The tables have been preloaded and no new data is created during  
> the test. Querying is done via dirty_match_object/1.
>
> I've noticed that the memory footprint of the Erlang VM grows as long  
> as I leave my test running. The VM will start with a low memory  
> footprint, say around 3-4 MB, and then grow to over 360 MB in the  
> space of a minute. I know I could use ets or dets directly and  
> probably workaround this issue but I'm intrigued and I'd like to  
> understand exactly what's happening.
>
> erlang:memory/0 reports this after a typical test run:
>
> [{total,385341784},
>   {processes,694596},
>   {processes_used,686596},
>   {system,384647188},
>   {atom,402833},
>   {atom_used,372656},
>   {binary,13728},
>   {code,2993679},
>   {ets,380521792}]

  what does erlang:memory/0 say before the run? what does
  mnesia:table_info(,memory/size) say? what does the test code look
  like?

  mats



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