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From: Po Lu <luangruo@yahoo.com>
To: Stefan Kangas <stefankangas@gmail.com>
Cc: Emacs developers <emacs-devel@gnu.org>,  tyler@tdodge.consulting
Subject: Re: "Significant Garbage Collection Improvement For Emacs" - sweep_conses performance improved by 50%?
Date: Sat, 29 Oct 2022 13:41:40 +0800	[thread overview]
Message-ID: <871qqr425n.fsf@yahoo.com> (raw)
In-Reply-To: <CADwFkmnT04otjCHxSi1dZHDr4yApA8h-_MbEH6nT7uy64vpcxQ@mail.gmail.com> (Stefan Kangas's message of "Sat, 29 Oct 2022 07:07:25 +0200")

Stefan Kangas <stefankangas@gmail.com> writes:

> In this blog post
>
> https://tdodge.consulting/blog/living-the-emacs-garbage-collection-dream
>
> the author asserts that a one-line patch "reduces the total wall clock
> duration for sweep conses execution by approximately 50%", at least in
> one benchmark.  There are some caveats; read the blog post for the
> full story.

My guess is that the blog post overestimates the performance cost of
branch predictor misses, and underestimates the real effect of the
change, which is making sweep_conses walk an array more and a linked
list less.  Which is also more cache friendly, but sweeping any kind of
array is intrinsically faster than doing the same to a linked list for
any number of other reasons.

I don't know what the memory consumption impact of such a change would
be since I haven't tried it myself.



  parent reply	other threads:[~2022-10-29  5:41 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-10-29  5:07 "Significant Garbage Collection Improvement For Emacs" - sweep_conses performance improved by 50%? Stefan Kangas
2022-10-29  5:19 ` Christopher Dimech
2022-10-29  5:41 ` Po Lu [this message]
2022-10-29  6:07   ` Tyler Dodge
2022-10-29 14:32     ` Stefan Monnier
2022-10-30  0:53       ` Po Lu
2023-02-11 20:10     ` Ihor Radchenko
2023-02-12 21:58       ` Konstantin Kharlamov
2023-02-13 20:07         ` Konstantin Kharlamov

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