Re: MPS: Forwording symbols

[Gerd Möllmann]

Helmut Eller <eller.helmut@gmail.com> writes:

> On Mon, Jun 17 2024, Gerd Möllmann wrote:
>
>> The whole dumping of these structs looks highly dubious to me,
>> independent of MPS. They are constants, always have been, AFAICT, even
>> from what I remember from the 90s.
>
> The patch below creates the necessary relocs so that no forwarding
> structs end up in the dump.

Thanks. pushed.

>
>> Looking forward to the time when the mirror code is gone :-).
>
> I'm not so optimistic.  The first collection is very slow:
>
>    time ./emacs -batch -f igc--collect
>    
>    real    0m12.555s
>    user    0m11.708s
>    sys     0m0.097s

That's pretty slow, indeed. The version of Emacs I'm currently running,
which is my fork which does not contain your recent changes, and is an
optimized build with -lmps says

.../emacs/github/igc % /usr/bin/time src/emacs -batch -f igc--collect
        0.25 real         0.14 user         0.11 sys

> That's not good.  Maybe there is some unfixed problem that is causing
> this slowness, but it could also be that MPS simply is so slow for this
> allocation pattern.

I guess it is what you suspect because I run into an assertion when dumping:

  Dumping fingerprint: 
79b503a407de48b18f4c304971c234d89bf236c259a1e7cd857559f919943b91

  igc.c:345: Emacs fatal error: assertion failed: h->obj_type == IGC_OBJ_PAD || 
nbytes >= sizeof (struct igc_fwd)
  Fatal error 6: Aborted

That's a build starting from git clean -xdf, optimized, -lmps, and no
native compilation here of course.

I'll try to debug this, but I think I have to read the new code first a
bit to understand where to start.