Performance of lexical closures in interpreted code? (was Re: Execution speed)

[Phil Sainty <psainty@orcon.net.nz>]

Tangentially, that performance hit on the interpreted recursive
code with lexical-binding enabled is pretty severe!  From well under
2 seconds (with dynamic binding) to well over 4 seconds (with lexical
binding) in all my results.

Is this a known/accepted trade-off for the better byte-compiled
performance?  I'm assuming it's to do with overheads of lexical
closures.

The output npostavs generates indicates that it's largely (if
not solely) on account of a vast quantity of garbage collection.
Perhaps that is all the lexical environments being cleaned up?
(Although I would have thought that was a requirement for the
byte-compiled code as well, so I'm very much guessing.)

Can that be improved, or is this most likely to remain this way?




On 20/03/17 11:49, Phil Sainty wrote:
> Using npostavs's code:
> 
>      | DYNAMIC   | interpreted              | compiled
> --------------------------------------------------------------------
> 25.2 | recursive | 1.55s                    | 0.94s
>      | iterative | 1.70s                    | 1.06s
> --------------------------------------------------------------------
> 25.1 | recursive | 1.53s                    | 0.95s
>      | iterative | 1.87s                    | 1.06s
> --------------------------------------------------------------------
> 24.5 | recursive | 1.65s                    | 1.24s
>      | iterative | 1.43s                    | 0.95s
> --------------------------------------------------------------------
> 24.4 | recursive | 1.78s                    | 1.25s
>      | iterative | 1.59s                    | 1.02s
> --------------------------------------------------------------------
> 
> 
>      | LEXICAL   | interpreted              | compiled
> --------------------------------------------------------------------
> 25.2 | recursive | 4.27s (2.22s in 506 GCs) | 0.64s (0.03s in 6 GCs)
>      | iterative | 1.56s (0.10s in 23 GCs)  | 0.49s (0.03s in 6 GCs)
> --------------------------------------------------------------------
> 25.1 | recursive | 4.26s (2.21s in 506 GCs) | 0.64s (0.03s in 6 GCs)
>      | iterative | 1.58s (0.10s in 23 GCs)  | 0.50s (0.03s in 6 GCs)
> --------------------------------------------------------------------
> 24.5 | recursive | 4.11s (2.14s in 507 GCs) | 0.92s (0.03s in 6 GCs)
>      | iterative | 1.57s (0.09s in 22 GCs)  | 0.84s (0.03s in 7 GCs)
> --------------------------------------------------------------------
> 24.4 | recursive | 4.20s (2.08s in 506 GCs) | 0.91s (0.03s in 6 GCs)
>      | iterative | 1.65s (0.10s in 23 GCs)  | 0.82s (0.03s in 6 GCs)
> --------------------------------------------------------------------