From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Ihor Radchenko Newsgroups: gmane.emacs.devel Subject: Re: Bignum performance (was: Shrinking the C core) Date: Fri, 11 Aug 2023 12:32:42 +0000 Message-ID: <87msyxoj2t.fsf@localhost> References: <20230809094655.793FC18A4654@snark.thyrsus.com> <87il9owg0f.fsf@yahoo.com> <83fs4rjq9j.fsf@gnu.org> <87jzu2tvfc.fsf@dataswamp.org> <87y1ih3mc1.fsf@localhost> <87h6p5kcek.fsf@dataswamp.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="23713"; mail-complaints-to="usenet@ciao.gmane.io" Cc: emacs-devel@gnu.org To: Emanuel Berg Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Fri Aug 11 14:33:10 2023 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 1qURKH-0005wc-6d for ged-emacs-devel@m.gmane-mx.org; Fri, 11 Aug 2023 14:33:09 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qURJb-0005LF-AI; Fri, 11 Aug 2023 08:32:27 -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 1qURJX-0005Ko-BC for emacs-devel@gnu.org; Fri, 11 Aug 2023 08:32:23 -0400 Original-Received: from mout02.posteo.de ([185.67.36.66]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qURJU-0000nz-LD for emacs-devel@gnu.org; Fri, 11 Aug 2023 08:32:23 -0400 Original-Received: from submission (posteo.de [185.67.36.169]) by mout02.posteo.de (Postfix) with ESMTPS id 8B413240106 for ; Fri, 11 Aug 2023 14:32:17 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=posteo.net; s=2017; t=1691757137; bh=TXZYAttsTt2LijNhgXI6CnwyoRZqlFYi4UuQt1DnYdI=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version:From; b=Rx/rMyWAOMVKqHXmsynKsJnaO0uStEKZPNj+2gHzQzJ9U6ZHl0X2gpogHG09vaga3 C+PtWeW/JzW4L4LSiBg49KPdSnyQt9MMmdWZ5yfPFRsBjHJJmblieR+MN+BQJsO2ZZ SXuFqaLs0WmOPVhit597xBGT/JdPHSwhoaPdS1cUzsenx9A3MtOUO6XJ+CO2+FVpyG phnss5buAud3oaZMnAz8kz+jcfj9gvJz0m+7I/M8npIwgLRA/mlTZGxZg0UQ35nhxq 3ZzwXIUz0w/XWNVpgG/GLhsNB6OHNO1gLLh7/oIiHAWOZeNIt17LIN9V0k1+G0fdjR A9GpSCngLrmbg== Original-Received: from customer (localhost [127.0.0.1]) by submission (posteo.de) with ESMTPSA id 4RMjq45g30z6tvx; Fri, 11 Aug 2023 14:32:15 +0200 (CEST) In-Reply-To: <87h6p5kcek.fsf@dataswamp.org> Received-SPF: pass client-ip=185.67.36.66; envelope-from=yantar92@posteo.net; helo=mout02.posteo.de X-Spam_score_int: -43 X-Spam_score: -4.4 X-Spam_bar: ---- X-Spam_report: (-4.4 / 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, RCVD_IN_DNSWL_MED=-2.3, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, 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: 2.1.29 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:308576 Archived-At: Emanuel Berg writes: >> perf record emacs -Q -batch -l /tmp/fib.eln >> >> perf report: >> >> Creating bignums: >> 40.95% emacs emacs [.] allocate_vectorlike >> GC: >> 20.21% emacs emacs [.] process_mark_stack >> ... >> My conclusion from this is that big number implementation is >> not optimal. Mostly because it does not reuse the existing >> bignum objects and always create new ones - every single >> time we perform an arithmetic operation. > > Okay, interesting, how can you see that from the above data? process_mark_stack is the GC routine. And I see no other reason to call allocate_vectorlike so much except allocating new bignum objects (which are vectorlike; see src/lisp.h:pvec_type and src/bignum.h:Lisp_Bignum). > So is this a problem with the compiler? Or some > associated library? GC is the well-known problem of garbage-collector being slow when we allocate a large number of objects. And the fact that we allocate many objects is related to immutability of bignums. Every time we do (setq bignum (* bignum fixint)), we abandon the old object holding BIGNUM value and allocate a new bignum object with a new value. Clearly, this allocation is not free and takes a lot of CPU time. While the computation itself is fast. Maybe we could somehow re-use the already allocated bignum objects, similar to what is done for cons cells (see src/alloc.c:Fcons). -- Ihor Radchenko // yantar92, Org mode contributor, Learn more about Org mode at . Support Org development at , or support my work at