The Emacs dumper dispute [LWN.net]

The Emacs dumper dispute

Posted Dec 4, 2016 9:25 UTC (Sun) by eliz (guest, #94829)
In reply to: The Emacs dumper dispute by nix
Parent article: The Emacs dumper dispute

> On those platforms, Emacs uses its own malloc() implementation, which is an ancient malloc from the early 90s

This is factually incorrect: Emacs only uses its own malloc implementation during dumping. The dumped emacs executable uses the native malloc implementation on all the platforms mentioned in the previous post.

> It should rely on the documented malloc() interface, sans ridiculous dumping hooks, and serialize for dumping. That Eli doesn't understand that this is obviously the only even vaguely maintainable approach is baffling to me.

In fact, Eli understands this simple fact very well. There's never been any question that unexec should go. The issue at hand is what is the best alternative to unexec, with all its problems.

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The Emacs dumper dispute

Posted Dec 8, 2016 17:55 UTC (Thu) by nix (subscriber, #2304) [Link]

> This is factually incorrect: Emacs only uses its own malloc implementation during dumping. The dumped emacs executable uses the native malloc implementation on all the platforms mentioned in the previous post.

Really? Last time I tried to trace through the bugger it spotted the lack of malloc_set_state() and fell back to gmalloc for everything from dumping onwards, with fairly nasty consequences for memory usage. If the nasty consequences only relate to the relatively small amount of state stored during dumping, I'm fairly mystified as to how multi-hundred-MiB variances could be so apparent -- but Emacs is such a dynamic system that maybe I was being misled by perfectly normal run-to-run variability.