[erlang-questions] Big RAM Erlang stories/wisdom/anecdotes?

Valentin Micic <>
Sun Sep 27 23:25:48 CEST 2009


> Does anyone have war stories about big RAM machines (more than 16GB,
> for instance) + Erlang where you wish that the heap steps were a bit
> smaller?

One of our systems is using a few machines with 128 GB RAM each, and quite
uneventfully so. In order to maximize memory used by ETS, we've used
binaries that are up to 64 octets long, or rather, we're storing a simple
two-tuple binaries, one is 20 octet key, and another holds everything else
within 64 octets (also contains some room for growth). We had to do a few
specialized term-to-binary-to-term conversions to support this, but CPU cost
for this turned to be minimal.

Why 64-octets? Well, during the testing we picked up that if one exceeds 64
octets, additional 64+change octets would have been allocated from heap
without releasing 64 octets that have been already allocated for that entry
by ETS. We've never had time to get to the bottom of this, so we just
decided to use 64 bytes instead. Additional programming proved to be
trivial.

V/



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