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Re: Preview: portable dumper

From: Daniel Colascione
Subject: Re: Preview: portable dumper
Date: Mon, 12 Feb 2018 12:18:36 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.0

On 10/19/2017 03:12 AM, Jeremie Courreges-Anglas wrote:
On Wed, Oct 18 2017, Kaushal Modi <address@hidden> wrote:

Just bumping the thread. Would like to know what came out of this.

Same here.  I don't really care whether the portable dumper or the "big
.elc file" approach is taken, but it would be cool to see emacs out of
the malloc and unexec business.  This code is fragile and tends to break
on less popular platforms (OpenBSD in my case).

I've pushed the portable dumper to the pdumper Savannah branch. It should support a fully PIC Emacs.

I implemented demand-paging logic and backed all of it out: the demand paging worked fine, but I wasn't able to figure out a good way to get GC not to page in the whole region almost immediately anyway. I was surprised to find that my Emacs GCs almost immediately after start.

Timing on the current code is nevertheless pretty good. Running emacs -Q -nw -batch --eval '(progn (garbage-collect) (kill-emacs))' 100 times,

  unexec: 22.47ms per invocation
  pdumper: 28.19ms per invocation

I think this degree of startup overhead is acceptable.

I could implement the non-PIC mode I'd previously mentioned; I'm confident it would be faster than unexec. But with PIC doing this well, why bother? We want a PIC Emacs for security reasons anyway.

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