From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: Tooltips GC overhead Date: Fri, 07 Aug 2015 18:23:10 +0300 Message-ID: <83vbcrqg0x.fsf@gnu.org> References: <55B7796B.3070005@gmx.at> <55B87E3F.80708@gmx.at> <55B8E367.9020201@cs.ucla.edu> <55B8F3E9.5000707@gmx.at> <833806yld0.fsf@gnu.org> <55B915CE.7070803@gmx.at> <55B94267.5050208@cs.ucla.edu> <55BCA454.6050208@gmx.at> <83egjkv2st.fsf@gnu.org> <83twsfu6b5.fsf@gnu.org> <83si7ztc6y.fsf@gnu.org> Reply-To: Eli Zaretskii NNTP-Posting-Host: plane.gmane.org X-Trace: ger.gmane.org 1438961017 18066 80.91.229.3 (7 Aug 2015 15:23:37 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 7 Aug 2015 15:23:37 +0000 (UTC) Cc: rudalics@gmx.at, eggert@cs.ucla.edu, emacs-devel@gnu.org To: Stefan Monnier Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Fri Aug 07 17:23:29 2015 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1ZNjUU-00045Y-9V for ged-emacs-devel@m.gmane.org; Fri, 07 Aug 2015 17:23:26 +0200 Original-Received: from localhost ([::1]:49533 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZNjUT-0006M3-LZ for ged-emacs-devel@m.gmane.org; Fri, 07 Aug 2015 11:23:25 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:60780) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZNjUN-0006HA-GO for emacs-devel@gnu.org; Fri, 07 Aug 2015 11:23:23 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZNjUI-0000Pi-NL for emacs-devel@gnu.org; Fri, 07 Aug 2015 11:23:19 -0400 Original-Received: from mtaout26.012.net.il ([80.179.55.182]:55792) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZNjUI-0000MX-A3 for emacs-devel@gnu.org; Fri, 07 Aug 2015 11:23:14 -0400 Original-Received: from conversion-daemon.mtaout26.012.net.il by mtaout26.012.net.il (HyperSendmail v2007.08) id <0NSP00G00XCK7500@mtaout26.012.net.il> for emacs-devel@gnu.org; Fri, 07 Aug 2015 18:26:39 +0300 (IDT) Original-Received: from HOME-C4E4A596F7 ([87.69.4.28]) by mtaout26.012.net.il (HyperSendmail v2007.08) with ESMTPA id <0NSP00FHZXKEXN10@mtaout26.012.net.il>; Fri, 07 Aug 2015 18:26:39 +0300 (IDT) In-reply-to: X-012-Sender: halo1@inter.net.il X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6.x X-Received-From: 80.179.55.182 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.14 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.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:188554 Archived-At: > From: Stefan Monnier > Cc: rudalics@gmx.at, eggert@cs.ucla.edu, emacs-devel@gnu.org > Date: Fri, 07 Aug 2015 10:52:34 -0400 > > > Just looking at the implementation of Fcons, I find it hard to believe > > a single comparison can have any significant effect on its efficiency. > > So I'm unsure how this could be of any practical concern. > > Fcons is a core operation executed fairly frequently, so any slowdown > (no matter how small) needs to be justified by a major advantage. Without some kind of quantitative criterion, this sounds irrational to me. Would a 0.001% slow-down be acceptable? How about 0.1%? There must exist some threshold below which any slow-down can be ignored, and the question I'm asking is what is that threshold? > >> > In any case, it's much better than the current useless profile. > >> I'm not convinced it'd make it sufficiently better > > Well, it allowed me in this case to identify the source of the problem > > quickly, efficiently, and accurately. > > IIUC, something *else* allowed you to do that. That something else was a watchpoint put on the variable, followed by semi-manual computation of the frequency distribution of functions that caused the watchpoint to fire. That's exactly what a profiler would have done for me, if it were looking at that variable instead of counting calls to malloc. > Until I have positive proof that the extra precision is useful in some > cases, I'll reject such changes in the default build. So it's either > "rejected" or "depends on a compile-time option" for now. Too bad.