[Tarantool-patches] [PATCH] net.box: allow to store user-defined fields in future object

Igor Munkin imun at tarantool.org
Thu Aug 12 21:13:56 MSK 2021


Thanks for the patch! I am curious why Lua tables are not chosen for
storing users data? It looks more natural (kinda netbox request storage
that would be similar to the fiber's one), and easier to implement. Of
course the only thing bothering me about Lua tables usage is Lua GC
pressure. However:
* Whether there are *too* much entries, TABOV might occur for REGISTRY
  table and keeping many tables (especially short living ones) at once
  is also not such good option.
* In case there are *just* much entries, I perhaps that REGISTRY
  performance is better that spawning lots of tables. Anyway, I haven't
  look on the mhash implementation, so I have no estimations about its
  perfomance. I see they are created and destroyed manually, but Lua
  tables are within the GC reign, so some time is spent on their
  traversal. At the same time, REGISTRY traversal is atomic, so
  inflating it also affects the time spent on a particular incremental
  GC step. Too much theory, BTW. Benchmarks are required for this case.
* If this is more an exceptional option (that's I doubt considering
  Yaroslav complains regarding this functionality breakage), then any of
  the option is fine IMHO, so the most convenient is preferable.

It would be great to see the comparison for your current implementation
and the one using Lua tables. The most interesting workload is a bunch
of short-term requests, I guess.

Best regards,

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