Re: Safe GC timing

Apart from safety issues - which I will defer to others, like Martin…

I have found that unless you can ensure that the entirety of your test takes place in the same thread, your timings will be off.


> On Jun 18, 2026, at 03:21, Tim Bradshaw (as tfb at tfeb dot org) <[email protected]> wrote:
> 
> I'm writing a macro to compute GC times (in several implementations, hence I'm only returning total time).
> 
> The guts of it for LW looks like
> 
> (let ((reset nil))
>  (unwind-protect
>      (progn
>        (enable-gc-timing)
>        (multiple-value-prog1
>            (values (funcall f) (getf (get-gc-timing :reset t) ':total) t)
>          (setf reset t)))
>    (unless reset
>      (get-gc-timing :reset t))))
> 
> Is this a safe approach?  It's obviously not going to compose with anything else which wants to time the GC.
> 
> --tim
> 	
> 
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