beating mnesia to death (was RE: Using 4Gb of ram with Erlang VM)

Ulf Wiger (AL/EAB) ulf.wiger@REDACTED
Wed Nov 9 00:00:02 CET 2005


To sum up my experiences on the 16 GB machine:

- 64-bit erlang seems to work like a charm
- I stored 70 million records in a table in 
  one benchmark (15 GB of RAM usage), and 
  built a 5-million record replicated disc_copies
  table in another. Everything worked pretty 
  much as expected, which was more than I 
  expected, actually(*).  ;-)
- Loading 5 million records from disk took about
  27 seconds; loading over the network took 
  about as long. Building the table from 
  scratch took over two hours.
- I ran 6 million simultaneous processes; 20 M
  when I used hibernate/3. Spawn and send times
  were unaffected.

My main gripe is that erlang terms take up
a huge amount of space on the heap, e.g. 
16 bytes per character in a string -- not 
particularly sexy. In order to get large
amounts of data in there, you pretty much
have to use binaries.


(*) I know that OTP doesn't have this type
of hardware in their lab, so this stuff isn't
really tested before release. Nice then to see
that it works exactly as advertised.

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