From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.ciao.gmane.io!not-for-mail From: Alan Mackenzie Newsgroups: gmane.emacs.devel Subject: Re: Correct line/column numbers in byte compiler messages Date: Sat, 21 Mar 2020 20:19:54 +0000 Message-ID: <20200321201954.GB7805@ACM> References: <20200319203449.GA4180@ACM> <20200320191846.GA5255@ACM> <20200321153041.GA7805@ACM> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: ciao.gmane.io; posting-host="ciao.gmane.io:159.69.161.202"; logging-data="99182"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Mutt/1.10.1 (2018-07-13) Cc: Rocky Bernstein , Stefan Monnier , emacs-devel To: Andrea Corallo Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sat Mar 21 21:20:39 2020 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 1jFkbn-000Phm-1W for ged-emacs-devel@m.gmane-mx.org; Sat, 21 Mar 2020 21:20:39 +0100 Original-Received: from localhost ([::1]:40524 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jFkbl-0002Gx-W2 for ged-emacs-devel@m.gmane-mx.org; Sat, 21 Mar 2020 16:20:38 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:47152) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jFkb9-0001V2-0s for emacs-devel@gnu.org; Sat, 21 Mar 2020 16:20:00 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jFkb7-0001tm-ST for emacs-devel@gnu.org; Sat, 21 Mar 2020 16:19:58 -0400 Original-Received: from colin.muc.de ([193.149.48.1]:58647 helo=mail.muc.de) by eggs.gnu.org with smtp (Exim 4.71) (envelope-from ) id 1jFkb7-0001ss-J2 for emacs-devel@gnu.org; Sat, 21 Mar 2020 16:19:57 -0400 Original-Received: (qmail 11665 invoked by uid 3782); 21 Mar 2020 20:19:55 -0000 Original-Received: from acm.muc.de (p2E5D577B.dip0.t-ipconnect.de [46.93.87.123]) by colin.muc.de (tmda-ofmipd) with ESMTP; Sat, 21 Mar 2020 21:19:54 +0100 Original-Received: (qmail 7647 invoked by uid 1000); 21 Mar 2020 20:19:54 -0000 Content-Disposition: inline In-Reply-To: X-Delivery-Agent: TMDA/1.1.12 (Macallan) X-Primary-Address: acm@muc.de X-detected-operating-system: by eggs.gnu.org: FreeBSD 9.x [fuzzy] X-Received-From: 193.149.48.1 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.23 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:245640 Archived-At: Hello, Andrea. On Sat, Mar 21, 2020 at 18:37:13 +0000, Andrea Corallo wrote: > Have to apologize this is probably the quarantine effect .... As of today, we're under quarantine, too. :-( > .... but I couldn't resist testing this: > #+BEGIN_SRC lisp > ;; -*- lexical-binding: t; -*- > (require 'cl-lib) > (defvar elb-list (cl-loop for i from 0 to 1500000 > if (cl-oddp i) > collect 'a > else > collect 'b)) > (defun elb-eq () > (let ((n 0)) > (dolist (l elb-list n) > (when (eq 'b l) > (cl-incf n))))) > (defun elb-eq-entry () > (dotimes (_ 1000) > (elb-eq))) > #+END_SRC > Results: > b619777dd6 (baseline) 50.09s > accurate-warning-pos 51.28s > This is about 2% perf penalty. On my Ryzen, I'm seeing a 50% penalty. :-( (Admittedly that's comparing the year old branch to current master. I suppose I should build the correct comparable revision and try again.) This suggests that the branch prediction logic isn't present (or isn't active) on the Ryzen. > Interestingly with the __builtin_expect trick applied exec time gets > back to 50.65s. How do you do this? I couldn't make much sense of the documentation of __builtin_expect. :-( > We could probably find a benchmark that better highlights the difference > (this is potentially dominated by cache misses while pointer chasing the > list) but is it worth? Could I ask you to do the following timing. Evaluate the following (e.g. in *scratch*): ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; (defmacro time-it (&rest forms) "Time the running of a sequence of forms using `float-time'. Call like this: \"M-: (time-it (foo ...) (bar ...) ...)\"." `(let ((start (float-time))) ,@forms (- (float-time) start))) (defun time-scroll (&optional arg) (interactive "P") (message "%s" (time-it (condition-case nil (while t (if arg (scroll-down) (scroll-up)) (sit-for 0)) (error nil))))) ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; , visit .../emacs/src/xdisp.c, and do M-: (time-scroll). This scrolls through the buffer and prints a timing in the minibuffer. (N.B. to run this again, type something at BOB and undo it, thus marking the fontification as stale.) I'm seeing 19.4s vs. 22.2s, which is around 15% difference. :-( > Regards > Andrea > -- > akrl@sdf.org -- Alan Mackenzie (Nuremberg, Germany).