Re: How strict is Lua in honoring collectgarbage() and its subcommands?

[Philipp Janda <siffiejoe@...>]

Am 28.05.2015 um 22:01 schröbte Brigham Toskin:
> Hey all.

Hi!

> [...]
>
> Obviously os.clock has limitations–which I'm okay with, since I don't need
> exact profiling data–but how accurate is collectgarbage("count")? The
> manual says it returns usage in "K bytes", so to get the answer in megs I
> divide by 1024; is this a reasonable adjustment for what it's actually
> returning? Does Lua actually respect the "stop" subcommand? Is the perhaps
> an issue more of the allocator than the garbage collector? I could be
> leaking memory, but 40 MB seems excessive.

I get about 140 MB in the "Hash-linked" `foreach_sum8` test on a 64-bit 
machine.

> Thoughts? Am I approaching my measurements completely wrong?

For one, you are not measuring what you think you are measuring: The 140 
MB is the memory used by 800000 closures with 3 unique upvalues each, 
created by the `lvalues()` function. (That's why the `foreach_sum8` test 
takes two times more memory than the `foreach_sum4` test, and 8 times 
more memory than the `foreach_sum1` tests.) The list elements are just 
noise in comparison ...

Philipp