From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Omar Polo Newsgroups: gmane.emacs.devel Subject: Re: [PATCH] support for accessing CPU/core count (processor-count) Date: Sun, 10 Oct 2021 23:04:53 +0200 Message-ID: <8735p8d1lc.fsf@omarpolo.com> References: <87h7dpgues.fsf@omarpolo.com> <871r4tgp9o.fsf@omarpolo.com> <87o87xf5ag.fsf@omarpolo.com> <8735p8ensy.fsf@omarpolo.com> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="33364"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: mu4e 1.6.6; emacs 28.0.50 Cc: Campbell Barton , emacs-devel@gnu.org To: Arthur Miller Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sun Oct 10 23:15:46 2021 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 1mZgAb-0008Sh-17 for ged-emacs-devel@m.gmane-mx.org; Sun, 10 Oct 2021 23:15:45 +0200 Original-Received: from localhost ([::1]:57490 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mZgAZ-0002X7-Oh for ged-emacs-devel@m.gmane-mx.org; Sun, 10 Oct 2021 17:15:43 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:51118) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mZg9Y-0001mF-HW for emacs-devel@gnu.org; Sun, 10 Oct 2021 17:14:40 -0400 Original-Received: from mail.omarpolo.com ([144.91.116.244]:51220) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mZg9P-0000ZV-LH for emacs-devel@gnu.org; Sun, 10 Oct 2021 17:14:39 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=omarpolo.com; s=20200327; t=1633900468; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=XssKzv0VkUbRKkmCUtGYjG/PkmhS1FALYLkv4F2wsbk=; b=OPcBn74E0Z1j7RxvAxW4FRLOrodxk7RHcYEZFI7dwqauUXpYOjvuL18AzfqqMP5+x63hgg t3rmD4jdbC+h4nN5jxYCX/hnVbmm84qFDZRTHZYUS3LZ1HfVD+kW/7vMdmGfu7cgCy3XPP ua2v5PdBCPD55vXkl6BhpFo6/pOGyn8= Original-Received: from localhost (host-79-45-237-189.retail.telecomitalia.it [79.45.237.189]) by mail.omarpolo.com (OpenSMTPD) with ESMTPSA id 897f1ffb (TLSv1.3:TLS_AES_256_GCM_SHA384:256:NO); Sun, 10 Oct 2021 23:14:28 +0200 (CEST) Original-Received: from venera (localhost [127.0.0.1]) by localhost (OpenSMTPD) with ESMTP id 0d7e14cf; Sun, 10 Oct 2021 23:14:23 +0200 (CEST) In-reply-to: Received-SPF: pass client-ip=144.91.116.244; envelope-from=op@omarpolo.com; helo=mail.omarpolo.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, 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: 2.1.23 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:276698 Archived-At: Arthur Miller writes: > Omar Polo writes: > >> Arthur Miller writes: >> >>> [...] >>> And that is the beauty of having it as a Lisp function. You can just tweak it, >>> don't need to recompile entire Emacs :). >> >> I know I'm getting off-topic, but I just don't understand your point. I >> don't see how spawning a bunch of commands, checking their return code >> and parsing their output is better than a couple of lines of C that do >> the right thing depending on the platform (decided at compile time!) and >> get directly an int. > I don't undestand what you don't udnerstand :-) > > I don't know my man; what do you mean with "bunch of commands" and how you would > achieve this for all platforms with "couple of lines of C". > > Here you have it; based on Andreas code from comp.el. I have just chagned part > shell command on gnu/linux since it can fail dependning on flags. Of course you > get an int back, "directly" :). > > #+begin_src emacs-lisp > (declare-function w32-get-nproc "w32.c") > > (defun processor-count () > (cond ((executable-find "nproc") > (with-temp-buffer > (call-process (executable-find "nproc") nil t nil) > (string-to-number (buffer-string)))) > ((eq 'windows-nt system-type) > (w32-get-nproc)) > ((eq 'berkeley-unix system-type) > (string-to-number > (shell-command-to-string "sysctl -n hw.ncpu"))) > (t 1))) > #+end_src > > > Compare to original patch in C, and tell me how is doing same in C better than > doing it in Lisp? Your Lisp routine should > return an int directly. I don't see what is different there and what advantage C > will give you here; more than extra work to implement it and maintain it later on. > > To note here is that 'shell-command-to-string' is not recommended since it can > return "more", than what expected, depending on what flags are used to pass to > bash. I am not sure if it can also differ if user uses some other > shell. call-process should be fine. I don't have a bsd system to test though. > > I haven't used /proc/cpuinfo. It is a bit dependning on what is goal here: is it > to get number of "usable" cpus for spawning threads, or is it to get real > hardware number of cpus. The reason is that Emacs can run in a "restricted" > system such as a Docker environement where number of CPUs available can be > limited. /proc/cpuinfo (on linux kernel) records hardware number of cores but > nproc return "available" number. So you could have something like this: > > #+begin_src emacs-lisp > (declare-function w32-get-nproc "w32.c") > > (defun processor-hardware-count () > (cond ((eq 'gnu/linux system-type) > (with-current-buffer (find-file-noselect "/proc/cpuinfo") > (if (re-search-forward "cpu cores.*: " nil t) > (string-to-number (current-word)) > 1))) > ((eq 'windows-nt system-type) > (w32-get-nproc)) > ((eq 'berkeley-unix system-type) > (string-to-number > (shell-command-to-string "sysctl -n hw.ncpu"))) > (t 1))) > #+end_src > > Could be done with "-all" flag to nproc too, but I think reading /proc/cpuinfo > is faster. > >> I love lisp, don't get me wrong, and I actually prefer writing elisp >> rather than following the GNU C coding style (I love C too but GNU style >> hurts my eyes.) > > Trust me; if anyone I always vote for doing it in C; but this one is probably > not worth doing in C. I have no idea how suggested posix sysconf deals with > restricted environements either. > >> Sure, checking the number of cpus is not something that is done a lot, >> and I can't imagine a situation where it would be a bottleneck, but on >> the other hand, for the same argument, it's not something that needs to >> be tweaked often > > Do you want hardware count; logical cores (think hyperthreading); should it work > in restricted environments? Quite a few things to take into consideration, isn't > it? > > Hope you understand what I mean better after examples. Something tells me you > won't agree :-), but that is OK. I just present my opinion. I don't really want to start a pointless thread, so I hope I didn't sound annoying. If that's the case, I'm sorry. I kind of get your point, and as I sad before, I don't have opinions on this particular case. I'm still not sure how C can be more difficult to maintain than an elisp, as to my eyes they're equal. (yes, elisp has enormous advantages in most cases, I won't be ever writing a major mode in C for example, but this is not one of those IMHO). But I've never really contributed something significant to Emacs, and I spend almost all my free time hacking in C, so I'm kinda biased ;-) But I'd like to add a small correction to your example. The sysctl is not correct on OpenBSD (and maybe NetBSD too? I can't check.) It should read (shell-command-to-string "sysctl -n hw.ncpuonline || sysctl -n hw.ncp") or something equivalent, please refer to my reply to the OP for the HW_NCPUONLINE vs HW_NCPU on OpenBSD. Cheers :)