From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: noverlay branch Date: Fri, 07 Oct 2022 10:56:17 -0400 Message-ID: References: <1468ca31-1703-82a1-0c8c-be2c5b5674a7@gmail.com> <87r0zld0de.fsf@rfc20.org> <87edvki88a.fsf@rfc20.org> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="24682"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/29.0.50 (gnu/linux) Cc: Matt Armstrong , emacs-devel@gnu.org To: Gerd =?windows-1252?Q?M=F6llmann?= Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Fri Oct 07 17:29:48 2022 Return-path: Envelope-to: ged-emacs-devel@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 1ogpIJ-0006EI-NS for ged-emacs-devel@m.gmane-mx.org; Fri, 07 Oct 2022 17:29:47 +0200 Original-Received: from localhost ([::1]:58156 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ogpII-0004Sy-8g for ged-emacs-devel@m.gmane-mx.org; Fri, 07 Oct 2022 11:29:46 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:57782) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ogom3-0001ti-Hs for emacs-devel@gnu.org; Fri, 07 Oct 2022 10:56:27 -0400 Original-Received: from mailscanner.iro.umontreal.ca ([132.204.25.50]:35650) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1ogom1-0001je-9X for emacs-devel@gnu.org; Fri, 07 Oct 2022 10:56:26 -0400 Original-Received: from pmg1.iro.umontreal.ca (localhost.localdomain [127.0.0.1]) by pmg1.iro.umontreal.ca (Proxmox) with ESMTP id 56EEF100142; Fri, 7 Oct 2022 10:56:23 -0400 (EDT) Original-Received: from mail01.iro.umontreal.ca (unknown [172.31.2.1]) by pmg1.iro.umontreal.ca (Proxmox) with ESMTP id A81351000E7; Fri, 7 Oct 2022 10:56:21 -0400 (EDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=iro.umontreal.ca; s=mail; t=1665154581; bh=PQ94Bb3/MeikZdMAhUFw0pSxLcf3IBqrahAg+vABsEo=; h=From:To:Cc:Subject:In-Reply-To:References:Date:From; b=jxpaD+wU9ThkiNdTU850q7prJdZLbmf77WYgizSvR1E+EAvbaahEWvQxuqe1EqZRD CQDWjZFaZq3mnB9hG1+sVeAIsqBYgOyFRqboaRsHjxP/pT9Nf+fbNOrO7BGy9xkEL1 HwCiyNhsmjAb5pHzEZaa0KytDmYQWhDknUBfnbv7meoMkApXLMVkRQeKjmCdGurGd3 VlQigAjqvyY7KFQZ+vzOMfe7LGh7tzt2X/NLoSIF8Dqt5f/jmhfWk71mIWvHiPWB0m 8Q+auzyn8eUx8vADqEXMk+yFyzpKx9bcEjumuV66gEzqM7HK+qXEGqCkTq/+ma8QFl nB53oIs+inRLQ== Original-Received: from pastel (65-110-220-202.cpe.pppoe.ca [65.110.220.202]) by mail01.iro.umontreal.ca (Postfix) with ESMTPSA id 7A7D51204D7; Fri, 7 Oct 2022 10:56:21 -0400 (EDT) In-Reply-To: (Stefan Monnier's message of "Fri, 07 Oct 2022 09:33:47 -0400") Received-SPF: pass client-ip=132.204.25.50; envelope-from=monnier@iro.umontreal.ca; helo=mailscanner.iro.umontreal.ca X-Spam_score_int: -42 X-Spam_score: -4.3 X-Spam_bar: ---- X-Spam_report: (-4.3 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_MED=-2.3, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.io gmane.emacs.devel:297155 Archived-At: >>> I think in the context of this overlay work the performance difference >>> is not very significant, since the code is doing a lot of other stuff >>> while traversing the tree. >> I agree. I think NULL could be better in multi-threaded cases, as >> Stefan alluded to. > > The current code should be multi-thread safe (except for the global > iterator, of course), despite its use of a global sentinel node: there's > no need to synchronize anything when reading a read-only field or when > writing a write-only field. But indeed, while it might be safe, its performance in a multi-threaded situation (with multiple cores) might be affected, because of the cache-line granularity and because the CPUs can't know that those writes can be reordered (or even thrown away) since they will never be matched by a corresponding read. Stefan