From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Pip Cet <pipcet@gmail.com>
Cc: michael_heerdegen@web.de, npostavs@gmail.com, 36447@debbugs.gnu.org
Subject: bug#36447: 27.0.50; New "Unknown keyword" errors
Date: Tue, 09 Jul 2019 17:05:53 -0400 [thread overview]
Message-ID: <jwv7e8q6hra.fsf-monnier+emacs@gnu.org> (raw)
In-Reply-To: <CAOqdjBfcyOUjBdEbc+Xy-mO7gCEaxWgn+6mk3ti_pH16rjQ9RQ@mail.gmail.com> (Pip Cet's message of "Sat, 6 Jul 2019 15:08:08 +0000")
I think we should get Daniel's opinion on this.
Stefan
> On Sat, Jul 6, 2019 at 6:45 AM Eli Zaretskii <eliz@gnu.org> wrote:
>> > > Indeed. I'm attaching a proof of concept that we can simply freeze the
>> > > hash tables when dumping and thaw them when loading a dump, which
>> > > includes rehashing. Do you happen to know why it wasn't done that way?
>> >
>> > I'd guess it was to shorten the startup time by doing this rehashing lazily.
>>
>> The function pdumper-stats with show the time it took to load Emacs,
>> so the effect of this on the load time can be measured
>
> I'm measuring it directly, and it's more than I expected: about a
> millisecond, for 4,300 hash table entries. What we can't easily
> measure is how much the lazy rehashing code would slow us down anyway.
>
> For comparison, the entire time stored in pdumper-stats is 15 ms here.
>
> I don't think that's significant, because we'd probably end up
> rehashing most of the large hash tables anyway. We're saving some 250
> KB of space in the pdmp image, which was previously used for redundant
> information. (I'm surprised it's that much, but I guess pdumper
> relocations are fairly large?)
>
> I'm attaching a revised patch, which uses vectors rather than consed
> lists for both the key_and_value vector, avoiding a copy in the common
> case where there is more than one hash table entry, and for the list
> of hash tables. It still contains debugging/timing code.
>
> charset.c currently assumes hash table entries will stay at the same
> index in Vcharset_hash_table. I think that works okay in practice,
> because we don't shrink or reorder hash tables, but it was still a bit
> of a nasty surprise.
>
> This concept appears to work: modify pdumper to special-case hash
> tables and freeze/thaw them properly. You probably shouldn't dump hash
> tables with complicated user-defined hash functions.
>
> Both PURE_P and pdumper_object_p fail to distinguish between tables
> that were pure or impure before being dumped.
>
> This also fixes the bug that (hash-table-count dumped-hash-table) will
> return a negative number if no previous access to the hash table has
> happened, but of course we can fix that directly...
>
> Of course, we're still modifying purecopied information.
next prev parent reply other threads:[~2019-07-09 21:05 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-30 18:23 bug#36447: 27.0.50; New "Unknown keyword" errors Michael Heerdegen
2019-06-30 18:43 ` Eli Zaretskii
2019-06-30 21:44 ` Michael Heerdegen
2019-07-01 12:25 ` Noam Postavsky
2019-07-01 13:20 ` Pip Cet
2019-07-01 22:04 ` Michael Heerdegen
2019-07-02 1:59 ` Stefan Kangas
2019-07-02 14:17 ` Eli Zaretskii
2019-07-02 13:29 ` Pip Cet
2019-07-02 15:35 ` Michael Heerdegen
2019-07-02 16:20 ` Noam Postavsky
2019-07-02 22:50 ` Pip Cet
2019-07-03 11:57 ` Pip Cet
2019-07-05 1:59 ` Michael Heerdegen
2019-07-05 6:35 ` Pip Cet
2019-07-05 7:50 ` Eli Zaretskii
2019-07-05 8:12 ` Pip Cet
2019-07-05 8:25 ` Eli Zaretskii
2019-07-05 8:36 ` Pip Cet
2019-07-05 8:41 ` Eli Zaretskii
2019-07-05 9:09 ` Pip Cet
2019-07-05 12:23 ` Robert Pluim
2019-07-05 12:33 ` Eli Zaretskii
2019-07-05 13:41 ` Pip Cet
2019-07-05 18:00 ` Stefan Monnier
2019-07-05 18:07 ` Eli Zaretskii
2019-07-05 20:16 ` Stefan Monnier
2019-07-05 18:57 ` Pip Cet
2019-07-05 19:13 ` Eli Zaretskii
2019-07-05 20:21 ` Stefan Monnier
2019-07-05 21:52 ` Pip Cet
2019-07-05 22:10 ` Stefan Monnier
2019-07-06 6:45 ` Eli Zaretskii
2019-07-06 15:08 ` Pip Cet
2019-07-09 21:05 ` Stefan Monnier [this message]
2019-07-10 2:38 ` Eli Zaretskii
2019-07-10 3:19 ` Daniel Colascione
2019-07-10 15:01 ` Pip Cet
2019-07-10 17:16 ` Daniel Colascione
2019-07-10 20:14 ` Pip Cet
2019-07-06 15:32 ` Michael Heerdegen
2019-07-08 17:30 ` Lars Ingebrigtsen
2019-07-08 17:58 ` Pip Cet
2019-07-08 22:18 ` Lars Ingebrigtsen
2019-07-08 22:25 ` Noam Postavsky
2019-07-09 14:00 ` Pip Cet
2019-07-10 3:01 ` Daniel Colascione
2019-07-14 14:06 ` Noam Postavsky
2019-07-08 23:22 ` Stefan Monnier
2019-07-08 22:23 ` Michael Heerdegen
2019-07-09 15:43 ` Eli Zaretskii
2019-07-09 20:15 ` Stefan Monnier
2019-07-05 7:55 ` Katsumi Yamaoka
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