Status of LJ_GC64 on x64?

  • From: Geoff Leyland <geoff_leyland@xxxxxxxxxxx>
  • To: luajit@xxxxxxxxxxxxx
  • Date: Wed, 29 Jul 2015 10:53:35 +1200


How is progress on the LJ_GC64 on x64? About a month ago, it was possible to
build on x64, but without a JIT. Mike, are you able to comment on whether
you’re working on an LJ_GC64 version of the JIT, and if so, roughly when it
might be available?

I ask because I do some work with OpenStreetMap data, converting maps from
their native format to a compact node-arc representation of the road network
for routing. OpenStreetMap data is large, and even reading a small country
like NZ, I make an effort to put all of the data I can into memory above 4GB.
However, it’s useful to maintain some tables in Lua: things like a map from
Node IDs to Node indexes or addresses, and a map of strings used in street
names (to aid deduplication of the strings).

Trouble is, when you read larger countries and the entire map, even the Node ID
to index map starts to push on memory limits. Taking this out of a table and
into a structure I manage myself means losing a reasonable chunk of the things
Lua does that make the job easy. It’s certainly feasible, but at that point it
might be worth resorting to C.


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