From: Paul Eggert <eggert@cs.ucla.edu>
To: Stefan Monnier <monnier@IRO.UMontreal.CA>
Cc: emacs-devel@gnu.org
Subject: Re: Lisp_Marker size on 32bit systems
Date: Fri, 7 Sep 2018 12:04:16 -0700 [thread overview]
Message-ID: <0e358c21-1e67-32f9-d24b-fa039753a2de@cs.ucla.edu> (raw)
In-Reply-To: <jwv36ulsdut.fsf-monnier+emacs@gnu.org>
On 09/07/2018 05:16 AM, Stefan Monnier wrote:
> Where does this 20% slow down come from?
Ha! It was because the 16-byte alignment caused pure space to overflow,
which disabled GC. No wonder there was such a big performance difference.
I fixed that, and now the patch to shrink marker allocations from 32 to
24 bytes on x86 causes my standard benchmark (make compile-always) to
run only 1.0% slower, which is more reasonable. A microbenchmark of
running (make-marker) over and over again for 10,000,000 times runs 36%
slower (815 vs 597 ns for a single call). So it still looks like we
should be following GCC's max_align_t hint and using 16-byte alignment
on x86, even though this wastes memory.
Maybe we should be using 4 mark bits instead of 3?
next prev parent reply other threads:[~2018-09-07 19:04 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-06 0:41 Lisp_Marker size on 32bit systems Stefan Monnier
2018-09-06 6:51 ` Paul Eggert
2018-09-06 12:17 ` Stefan Monnier
2018-09-07 7:15 ` Paul Eggert
2018-09-07 8:05 ` Eli Zaretskii
2018-09-07 13:45 ` Paul Eggert
2018-09-07 14:12 ` GDB and compiler-operations (was: Lisp_Marker size on 32bit systems) Stefan Monnier
2018-09-07 14:23 ` Eli Zaretskii
2018-09-07 15:16 ` GDB and compiler-operations Andreas Schwab
2018-09-07 15:48 ` GDB and compiler-operations (was: Lisp_Marker size on 32bit systems) Paul Eggert
2018-09-07 15:58 ` GDB and compiler-operations Stefan Monnier
2018-09-07 17:11 ` Eli Zaretskii
2018-09-07 17:15 ` Paul Eggert
2018-09-07 19:59 ` Tom Tromey
2018-09-07 14:19 ` Lisp_Marker size on 32bit systems Eli Zaretskii
2018-09-07 16:27 ` Paul Eggert
2018-09-07 17:16 ` Eli Zaretskii
2018-09-07 18:13 ` Paul Eggert
2018-09-07 18:32 ` Eli Zaretskii
2018-09-07 19:05 ` Paul Eggert
2018-09-07 19:22 ` Eli Zaretskii
2018-09-07 12:16 ` Stefan Monnier
2018-09-07 19:04 ` Paul Eggert [this message]
2018-09-07 19:45 ` Stefan Monnier
2018-09-07 21:03 ` Paul Eggert
2018-09-08 1:54 ` Stefan Monnier
2018-09-08 3:04 ` Paul Eggert
2018-09-08 3:10 ` Stefan Monnier
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