bug#39413: 26.2; Emacs gets hung

[ISHIKAWA,chiaki]

On 2021/08/16 20:35, Eli Zaretskii wrote:
> > Cc: larsi@gnus.org, npostavs@gmail.com, 39413@debbugs.gnu.org,
> >   chiaki.ishikawa@ubin.jp
> > From: "ISHIKAWA,chiaki" <ishikawa@yk.rim.or.jp>
> > Date: Mon, 16 Aug 2021 08:27:01 +0900
> >
> > But if you look slightly above, you will notice CPU core #4 is used 100%
> > (!).
> > That is emacs process. No other process is running that earnestly at
> > that moment.
> If we believe everything these tools show us, maybe.  But those tools
> suffer from the same problem Emacs does on a busy system: the tool
> itself might not get CPU to update its data, so you actually see a
> snapshot of what it saw last time it did get CPU.
>
> > PS: I found profiler-cpu-* functions, but I don't think it is wise to
> > run them during GC since they seem to allocate vector tables. However,
> > taking a snapshot of strack trace every now and then during GC seems
> > attractive for my investigation to figure out WHERE in GC, the excessive
> > time is spent.
> Emacs built-in profiling will not help us here, because it cannot
> profile below Lisp primitives.

Very tough.
I will see what I can do and report back if anything interesting shows up.

(The last time I tried to see where the time was spent, GC was busy 
reclaiming |cons| cells.
May not mean much.

I can only recall the old paper and in an 16 GB environment (including 
OS),  we may see some bad behavior.
"


 Address/memory management for a gigantic LISP environment or, GC
 considered harmful

"
by Jon L. White

https://dl.acm.org/doi/abs/10.1145/800087.802797