GNU bug report logs - #45200
Wishlist: There should be a `malloc-trim' function

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Message #74 received at 45200 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: DJ Delorie <dj <at> redhat.com>
Cc: carlos <at> redhat.com, fweimer <at> redhat.com, monnier <at> iro.umontreal.ca,
 45200 <at> debbugs.gnu.org, Hi-Angel <at> yandex.ru
Subject: Re: bug#45200: [PATCH] Force Glibc to free the memory freed
Date: Tue, 26 Jan 2021 16:49:53 +0200

> From: DJ Delorie <dj <at> redhat.com>
> Cc: Hi-Angel <at> yandex.ru, 45200 <at> debbugs.gnu.org, monnier <at> iro.umontreal.ca,
>         carlos <at> redhat.com, fweimer <at> redhat.com
> Date: Mon, 25 Jan 2021 17:17:27 -0500
> 
> Eli Zaretskii <eliz <at> gnu.org> writes:
> > Thanks, but is it really a good idea to call malloc_trim each time we
> > free some chunk of memory?
> 
> malloc_trim() is very expensive relative to free(), partly because of
> what it needs to do, and partly because it flushes the fastbins cache.

How expensive?  Can you give some quantitative measure?

> If you call it every, say, 1000 iterations of free, that might suffice.
> Or perhaps after each GC run.

There's no guarantee that a full GC will call 'free', even though
that's quite likely.

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