From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: DJ Delorie Newsgroups: gmane.emacs.bugs Subject: bug#45200: [PATCH] Force Glibc to free the memory freed Date: Wed, 03 Feb 2021 23:26:45 -0500 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="9581"; mail-complaints-to="usenet@ciao.gmane.io" Cc: fweimer@redhat.com, carlos@redhat.com, hi-angel@yandex.ru, 45200@debbugs.gnu.org To: Stefan Monnier Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Thu Feb 04 05:27:10 2021 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1l7WEY-0002N4-7M for geb-bug-gnu-emacs@m.gmane-mx.org; Thu, 04 Feb 2021 05:27:10 +0100 Original-Received: from localhost ([::1]:60792 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1l7WEW-0005nQ-NK for geb-bug-gnu-emacs@m.gmane-mx.org; 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Wed, 03 Feb 2021 23:26:52 -0500 X-MC-Unique: ZTNyMHMTPaelbhIXB-w1Hw-1 Original-Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C4FFD107ACED; Thu, 4 Feb 2021 04:26:50 +0000 (UTC) Original-Received: from greed.delorie.com (ovpn-114-77.rdu2.redhat.com [10.10.114.77]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 7502C71C8B; Thu, 4 Feb 2021 04:26:47 +0000 (UTC) Original-Received: from greed.delorie.com.redhat.com (localhost [127.0.0.1]) by greed.delorie.com (8.14.7/8.14.7) with ESMTP id 1144Qj8g000797; Wed, 3 Feb 2021 23:26:46 -0500 In-Reply-To: (message from Stefan Monnier on Wed, 03 Feb 2021 23:19:40 -0500) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dj@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.io gmane.emacs.bugs:199266 Archived-At: Stefan Monnier writes: > [ I have no idea what "fastbins" are, but I'll nod along approvingly. ] https://sourceware.org/glibc/wiki/MallocInternals Fastbins are one of the caches layered on the core malloc code. > OK, so `malloc_trim` can do a more thorough job and discover that > there's indeed 200MB free at the top which malloc/free wouldn't > have noticed? I guess that makes sense. Yes. > PS: One last thing: I must say I'm surprised to see the amount of > effort that seems to be spent on trying to release that "top" free > memory. From where I stand, it seems that it will only very rarely > allow you to release any non-trivial amount of memory. Why bother? We have to keep track of the top of heap anyway, in order to grow it. Adding a check to shrink it is pretty trivial, and it's our *only* way to return memory to the system.