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On 2017-12-01 01:45 AM, Meepen wrote:
Could you at all update metatables on coroutine switch? it'd be faster if you used the metatables at all but would slow down minimally otherwise


Context switches instead of namespacing?

Hmm... Maybe. It wouldn't be easy, because with context switches, any mistake leaks the wrong context. With namespacing, that problem is pretty much non-existent.

I mean, what do modern CPUs and kernels use?

On Nov 30, 2017 6:17 PM, "Soni "They/Them" L." <fakedme@gmail.com <mailto:fakedme@gmail.com>> wrote:

    Hi!

    I have some code that looks like this:

    debug.setmetatable("", {__index=function(o,k)
      local mt = metatables[coroutine.running()].string
      if mt then
        local __index = rawget(mt, "__index")
        if type(__index) == "function" then
          return __index(o,k)
        else
          return __index[k]
        end
      end
      error()
    end})

    It takes the metatables for the basic Lua types (string, number,
    nil, etc) and replaces them with a proxy metatable. This proxy
    metatable forwards to a different table based on the currently
    running coroutine. This gives me virtualization of those metatables.

    It's really slow (3-4x slower[1] than the default string
    metatable) and I'd like to make it faster. Is that possible?

    [1] - I haven't actually benchmarked it, but default string
    metatable gives about 2 table accesses per operation; this thing
    does at least 8 when using globals, and that doesn't take into
    account interpreter overhead and all the function calls!

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