From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Andrea Corallo Newsgroups: gmane.emacs.devel Subject: Re: last_marked array is now ifdef'ed away Date: Mon, 16 Sep 2024 14:07:16 -0400 Message-ID: References: <86zfokyp64.fsf@gnu.org> <86ed5pkz53.fsf@gnu.org> <851C7C12-44A1-4661-9EA7-16B0B7209D11@gmail.com> <86a5gbk295.fsf@gnu.org> <8634m2f8ii.fsf@gnu.org> <86ldzte9qr.fsf@gnu.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="9624"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Cc: Stefan Kangas , mattias.engdegard@gmail.com, emacs-devel@gnu.org To: Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Mon Sep 16 20:07:56 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 1sqG8h-0002LV-JD for ged-emacs-devel@m.gmane-mx.org; Mon, 16 Sep 2024 20:07:55 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sqG88-00081Q-7x; Mon, 16 Sep 2024 14:07:20 -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 1sqG85-0007wm-Vh for emacs-devel@gnu.org; Mon, 16 Sep 2024 14:07:18 -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 1sqG85-0006mh-Jp; Mon, 16 Sep 2024 14:07:17 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=MIME-Version:Date:References:In-Reply-To:Subject:To: From; bh=1KUBvdVniKg7b/sq7nN3zL9n5f8u6xmXZ6M+W/FpjRk=; b=lWD11UHDsi99ZbD6iwsC bpSG+Fc00vbdFFem2F0T/p+es73nWRpZrKVdChw1dpbMCoNFKanzqliQFDDfiAPfo0lukfjPhBAPJ gTU+MT13J6FV6ZhyF3hzq6uoaROR67tVlv/nnEiQ++eT+kui23WwNnVjy2pvumo3wliIjWGXlotAO fckwOLRvpOxoj9lyVhGQzEnUIxDC3up4Oz/NUmzFAvYNqWu9KLrlAfaHtErkYgnN777M/8vGYgQdl mB42nCdseNjxJ8zI68h3g2Yc97yVCFseGhOqFuNPVP8X3GEoGs1NYqBp7p1TYmtRWeWbCHQoAXOwG xzfA1JsnFO4dXg==; Original-Received: from acorallo by fencepost.gnu.org with local (Exim 4.90_1) (envelope-from ) id 1sqG85-0001Z2-0X; Mon, 16 Sep 2024 14:07:17 -0400 In-Reply-To: <86ldzte9qr.fsf@gnu.org> (Eli Zaretskii's message of "Sun, 15 Sep 2024 09:01:16 +0300") 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:323672 Archived-At: Eli Zaretskii writes: >> From: Stefan Kangas >> Date: Sat, 14 Sep 2024 15:50:03 -0700 >> Cc: emacs-devel@gnu.org >> >> Eli Zaretskii writes: >> >> > I'm quite confident that I want this be turned on again. >> >> Since this affects performance by quite a bit (4.5-6.5 %, reportedly), >> how about the suggestion to "hitch it to another existing config option >> like ENABLE_CHECKING, or even make this an independent config option"? > > This feature is useless if it is optional, because its main (perhaps > the only) use is when Emacs crashes during GC on a user machine, > especially without enough debug info. Crashes during GC are rarely if > at all reproducible, so the only hope to investigate them is to look > at the objects recorded in the last_marked array, and asking users to > rebuild with some non-default option will not help. > > If we are going to make it a compilation option, we might as well > remove it entirely. > > 5% of slowdown during GC (if that's a well-established number) is a > small price to pay for the possibility of investigating rare crashes. > A typical GC cycle takes tens or hundreds of milliseconds, so these > few percents are just a couple of msec. 5% slowdown during GC is at worst 2.5% slowdown overall for GC intensive workloads. I think as well we should not loose this debug tool for a slowdown that no-one would notice. So I'm for re-enabling the code without it being under a default-off flag. Andrea