From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: last_marked array is now ifdef'ed away Date: Sun, 15 Sep 2024 08:51:11 +0300 Message-ID: <86o74pea7k.fsf@gnu.org> References: <86zfokyp64.fsf@gnu.org> <86ed5pkz53.fsf@gnu.org> <851C7C12-44A1-4661-9EA7-16B0B7209D11@gmail.com> <86a5gbk295.fsf@gnu.org> <8634m2f8ii.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="5755"; mail-complaints-to="usenet@ciao.gmane.io" Cc: emacs-devel@gnu.org To: Mattias =?utf-8?Q?Engdeg=C3=A5rd?= Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sun Sep 15 07:51:58 2024 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 1spiAv-0001Mo-Lc for ged-emacs-devel@m.gmane-mx.org; Sun, 15 Sep 2024 07:51:57 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1spiAD-0008Oi-TH; Sun, 15 Sep 2024 01:51:13 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1spiAC-0008OA-Ey for emacs-devel@gnu.org; Sun, 15 Sep 2024 01:51:12 -0400 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1spiAC-00047j-6O; Sun, 15 Sep 2024 01:51:12 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=MIME-version:References:Subject:In-Reply-To:To:From: Date; bh=hImogmNidvMeVnqLKWJm8T16de1WA7agM3ptKbnIqxE=; b=fe7AYeo8oizUo62rCIRV 9u1T41jgqWH9cSYjqLOb4uCVAh7DQZ8X9Oxz2c5OOMTlnRNFWVIHH2a8rKszEZsuI1//I2BXqGq0I g8ztne0iPsJbzWxP6ry+ZBP4wzO+Ds7ai9h/fk8auymCFA3ruC6JATBuH9ZOdZ1IFN2BC8qW9+bi+ d4yPn/BD2USTbpNYxuY/S+lUMk6bPuUbD3fVLhEbaw+g7IJslhO4xe17z8svgCtuCwRZNOnA6esq8 VhzWNFk+k4vJE7thRQ7ekNpZmXRW7vsvjS2Mahm4wKpSNEdJJyER943/ivKyGek3IVcVn6KZ4Qspc e/+eb1cVPtyiVA==; In-Reply-To: (message from Mattias =?utf-8?Q?Engdeg=C3=A5rd?= on Sat, 14 Sep 2024 22:30:11 +0200) 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-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.devel:323629 Archived-At: > From: Mattias Engdegård > Date: Sat, 14 Sep 2024 22:30:11 +0200 > Cc: emacs-devel@gnu.org > > 14 sep. 2024 kl. 19.30 skrev Eli Zaretskii : > > > That's the nature of things that are needed rarely. But when they > > _are_ needed, there's nothing to replace them, and that's when you > > appreciate their existence. Like safety belts, these features are > > never a waste. > > No, this device doesn't improve safety in any way. At best it's a special-purpose single-channel flight data recorder mounted in such a way that it disrupts the airflow and increases fuel consumption. Let's see if we can make it a bit more streamlined. I'm okay with FDR analogy. As anyone who saw Air Crash Investigation series knows, this is invaluable in investigating the (very rare!) airplane crashes. > > 16 is way too few. GC is deeply recursive, and when I used this, I > > almost always had to look at much more than 16 objects. > > Note that the GC recursion is now almost entirely handled by mark_stack. 512 entries is an entire x86 page; surely that can be trimmed? I'd need to see actual evidence for a shorter array, based on actual GC run of some data structure. Also, how bad is the penalty for accessing 512-element array vs a 16-element array? Unless it's close to 10% or exceeds that, I wouldn't bother.