220 13773 <8948B587-EFBF-476F-BBE2-DAEA00373AC1@gmail.com> article Path: news.gmane.org!not-for-mail From: David Krauss Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: Re: Stricter semantics for moved into objects with operator=(T&&) Date: Thu, 9 Oct 2014 11:57:53 +0800 Lines: 61 Approved: news@gmane.org Message-ID: <8948B587-EFBF-476F-BBE2-DAEA00373AC1@gmail.com> References: <567868a2-a0aa-4fb9-993e-0d2a27c11a73@isocpp.org> Reply-To: std-proposals@isocpp.org NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 (Mac OS X Mail 7.3 \(1878.6\)) Content-Type: multipart/alternative; boundary="Apple-Mail=_78983927-3BEB-4226-88F9-982B336EF5A7" X-Trace: ger.gmane.org 1412827096 5839 80.91.229.3 (9 Oct 2014 03:58:16 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 9 Oct 2014 03:58:16 +0000 (UTC) To: std-proposals@isocpp.org Original-X-From: std-proposals+bncBCW25A7E3QCRBT4P3CQQKGQEKPBWS4Y@isocpp.org Thu Oct 09 05:58:10 2014 Return-path: Envelope-to: gclcip-std-proposals@m.gmane.org Original-Received: from mail-yk0-f200.google.com ([209.85.160.200]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Xc4rh-0007QW-4z for gclcip-std-proposals@m.gmane.org; Thu, 09 Oct 2014 05:58:09 +0200 Original-Received: by mail-yk0-f200.google.com with SMTP id 200sf1946011ykr.11 for ; Wed, 08 Oct 2014 20:58:08 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:from:message-id:mime-version:subject:date :references:to:in-reply-to:x-original-sender :x-original-authentication-results:reply-to:precedence:mailing-list :list-id:list-post:list-help:list-archive:list-subscribe :list-unsubscribe:content-type; bh=tFE0NzKzcU73u69oucmn9Cbp7aoDjB1LPsqWwWKpjkA=; b=ZQM+3Zx3aERahwXTW4ZGZ+vsddvYZBbMzA56j9tIZP+UGwiuIYWjFykpLmS+LZ3BfS UOGDapAf55vWe1EO4KoCWpNW6kF6w5spW6wHiv2nvzQvAv9PSnMCop7IiRzjZZ/IF2P7 dCTzeBdLZ/iWgpsh8GmVoRMyjgc98d93znbfzw6Sz/xamy3NBEvzB/L18dZVTuOfg408 ZLLplb+oBsLsfdNBihQrC9oouYR5W1n0b7fBmE4/lXA3cwegwXv8XoLlC4zacgaGouV/ 1sEW4N54jG/CxnrOMxLQyPEqqesfDVCwWUrDtBzK/deNQ3JviB3W4FpwO1HCN2aah/pT 2FrA== X-Gm-Message-State: ALoCoQk99IPYB4GEGFfsXAY0RSGPuWqQbZeflAoSr3h1RyUBA92rx9PXP+pj777hez0Qt22DbWAN X-Received: by 10.236.41.102 with SMTP id g66mr9982876yhb.15.1412827088211; Wed, 08 Oct 2014 20:58:08 -0700 (PDT) X-BeenThere: std-proposals@isocpp.org Original-Received: by 10.50.4.8 with SMTP id g8ls1959609igg.42.canary; Wed, 08 Oct 2014 20:58:07 -0700 (PDT) X-Received: by 10.51.17.66 with SMTP id gc2mr4386986igd.40.1412827087681; Wed, 08 Oct 2014 20:58:07 -0700 (PDT) Original-Received: from mail-ig0-x229.google.com (mail-ig0-x229.google.com [2607:f8b0:4001:c05::229]) by mx.google.com with ESMTPS id my9si7549751icb.46.2014.10.08.20.58.07 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 08 Oct 2014 20:58:07 -0700 (PDT) Received-SPF: pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:4001:c05::229 as permitted sender) client-ip=2607:f8b0:4001:c05::229; Original-Received: by mail-ig0-f169.google.com with SMTP id uq10so1281456igb.4 for ; Wed, 08 Oct 2014 20:58:07 -0700 (PDT) X-Received: by 10.42.243.1 with SMTP id lk1mr3369595icb.51.1412827087254; Wed, 08 Oct 2014 20:58:07 -0700 (PDT) Original-Received: from [172.20.10.2] ([121.54.54.129]) by mx.google.com with ESMTPSA id oq6sm11607654igb.2.2014.10.08.20.58.04 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Wed, 08 Oct 2014 20:58:07 -0700 (PDT) In-Reply-To: <567868a2-a0aa-4fb9-993e-0d2a27c11a73@isocpp.org> X-Mailer: Apple Mail (2.1878.6) X-Original-Sender: potswa@gmail.com X-Original-Authentication-Results: mx.google.com; spf=pass (google.com: domain of potswa@gmail.com designates 2607:f8b0:4001:c05::229 as permitted sender) smtp.mail=potswa@gmail.com; dkim=pass header.i=@gmail.com; dmarc=pass (p=NONE dis=NONE) header.from=gmail.com Precedence: list Mailing-list: list std-proposals@isocpp.org; contact std-proposals+owners@isocpp.org List-ID: X-Google-Group-Id: 399137483710 List-Post: , List-Help: , List-Archive: List-Subscribe: , List-Unsubscribe: , Xref: news.gmane.org gmane.comp.lang.c++.isocpp.proposals:13773 Archived-At: --Apple-Mail=_78983927-3BEB-4226-88F9-982B336EF5A7 Content-Type: text/plain; charset=ISO-8859-1 On 2014-10-09, at 9:48 AM, Matthew Fioravante wrote: > At the end of this sequence, 3GB of memory will be in use and on a memory constrained system, this could cause an out of memory error simply because we used move semantics (which is supposed to be a optimization!) instead of copy. Whenever you actually need to free memory, you need to swap with an empty object. Even clear() won't do. Having capacity in moved-from or otherwise empty vectors is an important optimization, because they are likely to refer to hot cache lines. -- --- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. Visit this group at http://groups.google.com/a/isocpp.org/group/std-proposals/. --Apple-Mail=_78983927-3BEB-4226-88F9-982B336EF5A7 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=ISO-8859-1
On 2014&= ndash;10–09, at 9:48 AM, Matthew Fioravante <fmatthew5876@gmail.com> wrote:

At the end of this sequence, 3GB of memory will be in use and on a me= mory constrained system, this could cause an out of memory error simply bec= ause we used move semantics (which is supposed to be a optimization!) inste= ad of copy.

Whenever you actually need to = free memory, you need to swap with an empty object. Even clear() won’= t do.

Having capacity in moved-from or otherwise e= mpty vectors is an important optimization, because they are likely to refer= to hot cache lines.

--

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