From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: Concurrency via isolated process/thread Date: Fri, 07 Jul 2023 16:16:44 +0300 Message-ID: <83edljg8ub.fsf@gnu.org> References: <871qhnr4ty.fsf@localhost> <87sfa28ura.fsf@localhost> <87cz16o8vz.fsf@yahoo.com> <87jzve8r4m.fsf@localhost> <871qhmo5nv.fsf@yahoo.com> <87bkgq8p5t.fsf@localhost> <831qhmjwk0.fsf@gnu.org> <875y6y8nlr.fsf@localhost> <87h6qhnalc.fsf@yahoo.com> <87ilax71wo.fsf@localhost> <878rbtkz2c.fsf@yahoo.com> <87a5w96x2o.fsf@localhost> <87jzvdjjp4.fsf@yahoo.com> <877crd6w53.fsf@localhost> <877crdjiwn.fsf@yahoo.com> <874jmh6v4s.fsf@localhost> <83y1jtgmbw.fsf@gnu.org> <87zg49xfke.fsf@localhost> <83sfa1gjns.fsf@gnu.org> <87r0plxbep.fsf@localhost> <83ilawhpi6.fsf@gnu.org> <87zg48apwr.fsf@localhost> Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="14750"; mail-complaints-to="usenet@ciao.gmane.io" Cc: luangruo@yahoo.com, emacs-devel@gnu.org To: Ihor Radchenko Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Fri Jul 07 15:17:51 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 1qHlLK-0003bI-75 for ged-emacs-devel@m.gmane-mx.org; Fri, 07 Jul 2023 15:17:50 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qHlKL-0004ZF-Qk; Fri, 07 Jul 2023 09:16:49 -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 1qHlKJ-0004Yq-PD for emacs-devel@gnu.org; Fri, 07 Jul 2023 09:16:47 -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 1qHlKJ-0000Pm-D6; Fri, 07 Jul 2023 09:16:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=References:Subject:In-Reply-To:To:From:Date: mime-version; bh=S1WHV4eX6A4xMsy5HUVx62hJIUAzZOyU2dtXgrv5//U=; b=N7shbgCWdjQr /mMNBk9ih8xUxsE3QW+PHxhmkFy98zD9ah7t7enDpYlIB4BmNBzGOqckkSyeKbT8S0+cDvaoHtMjl XA6GNbWv8851rZlpfudZ09WxmF04ygyYPuhDyG5KOCPPJb0lcfVtMboly3lYf6zAQ8ywshu9J/7CQ Yn312DmOCccVx3jHnWgxKcBKUrPjBgVr/INqb9pgMpbjZ5xz/8THIfHB3HhBbBYdPuB9v7xyMwnAF 3861Sjxts+lKmahnPxqJjDblnj/MlqXoyTIjOxvyRQ8td1+6Zrs6zr06JVdTH8phEJEEpQwU60OVo 0RMljiecjDi0yDEY3voI7g==; Original-Received: from [87.69.77.57] (helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qHlKD-0007yG-Uq; Fri, 07 Jul 2023 09:16:47 -0400 In-Reply-To: <87zg48apwr.fsf@localhost> (message from Ihor Radchenko on Fri, 07 Jul 2023 12:04:36 +0000) 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:307568 Archived-At: > From: Ihor Radchenko > Cc: luangruo@yahoo.com, emacs-devel@gnu.org > Date: Fri, 07 Jul 2023 12:04:36 +0000 > > Eli Zaretskii writes: > > > GC doesn't only free memory used by dead objects. It also performs > > bookkeeping on live objects: compacts data of strings, relocates text > > of buffers, compacts the gap in buffers where it became too large, > > etc. This bookkeeping is more important when Emacs is short on > > memory: in those cases these bookkeeping tasks might mean the > > difference between being able to keep the session healthy enough to > > allow the user to shut down in an orderly fashion. > > What you are describing will only affect subr primitives that work > directly with C structs and address space. But that's how _everything_ works in Emacs. No Lisp runs except by calling primitives. > So, we can distinguish two locks: (1) low-level, only available to C > subroutines; (2) Elisp-level, where the lock merely prevents other Elisp > code from modifying the data. GC is safe to run when type-2 lock is in > place as it will never clear the data in use and never alter the data in > any way visible on Elisp level. Emacs doesn't know whether some C code which runs was invoked from C or from Lisp. (Basically, everything is invoked from Lisp, one way or another, as soon as we call recursive-edit from 'main' for the first time after startup.) > > Locking objects means these bookkeeping tasks will be disabled. That > > could adversely affect the available memory and the memory footprint > > in general. > > I do not think that it is that bad if we consider type-1 locks. There are no type-1 and type-2 locks. They are indistinguishable. > Let's consider the current thread to be thread 2 paused because thread 1 > is doing (setq i ...) at the same time and locked object corresponding > to obarray variable slot for "i". > > Thread 1 will continue executing until (very soon) it calls maybe_gc > itself. This time, no further object lock is active and gc may proceed, > continuing both the threads once GC is done. You are trying to solve what constitutes a very small, almost negligible, part of the problem. The elephant in the room is something else.