Re: Some experience with the igc branch

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 23 Dec 2024 16:03:53 +0000
> From: Pip Cet <pipcet@protonmail.com>
> Cc: Eli Zaretskii <eliz@gnu.org>, ofv@wanadoo.es, emacs-devel@gnu.org, eller.helmut@gmail.com, acorallo@gnu.org
> 
> --- a/src/igc.c
> +++ b/src/igc.c
> @@ -747,19 +747,41 @@ IGC_DEFINE_LIST (igc_root);
>  
>  /* Registry entry for an MPS thread mps_thr_t.  */
>  
> +#include <pthread.h>

We cannot use pthreads.h in portable code.  If we want to use threads,
we need separate implementations for Posix and Windows, like wedid in
systhread.c for Lisp threads.

> +struct emacs_ap
> +{
> +  mps_ap_t mps_ap;
> +  struct igc *gc;
> +  pthread_t allocation_thread;

pthread_t is non-portable, for the same reasons.

> This is the "slow path" only, used for all allocations. Will cause a
> great number of busy-looping threads.

A lot of threads might be problematic.  Each thread reserves memory
for its stack, so you end up with lots of reserved memory, and on
32-bit systems can run out of address space.

Why do we need this, again?