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: Pure space Date: Sat, 17 Aug 2024 14:06:47 +0300 Message-ID: <865xrz2yt4.fsf@gnu.org> References: <87cym8jngk.fsf@protonmail.com> <87r0ank1hq.fsf@yahoo.com> <87bk1rk0xm.fsf@yahoo.com> <87zfpbil13.fsf@protonmail.com> Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="38924"; mail-complaints-to="usenet@ciao.gmane.io" Cc: luangruo@yahoo.com, emacs-devel@gnu.org To: Pip Cet Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sat Aug 17 13:07:29 2024 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 1sfHHN-0009zC-Az for ged-emacs-devel@m.gmane-mx.org; Sat, 17 Aug 2024 13:07:29 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sfHGo-0000lm-9T; Sat, 17 Aug 2024 07:06:54 -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 1sfHGm-0000kG-Cv for emacs-devel@gnu.org; Sat, 17 Aug 2024 07:06:52 -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 1sfHGk-0000B0-TC; Sat, 17 Aug 2024 07:06:50 -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=AiyvPU1soXpl9sMmrTOFrbQ89+dW2IhF7LNDQtMDtGY=; b=Uuzjyyws6Lgm GDeyqUM5OP29kybKRscJfC1Ctal4eS6to57+c/iRj9OINCiViYlCkMqs/vq1U2iSxH0Jbxr8S4bCy f7g5M1QsbisQ4qYtJd1n1kiNT4X1F9dscCBDjlsJeSWd6l/5KTbHr9rxF6PC02+yV/o6uTQzRsci/ Edo5VhxCCIhDhHfCGuEO9EH8nkQxwxinqIfJDlzoSx3RKSX36gvbYZvkHVR93mxkaSkHv7IMpx8eH 9G2HPvNPMZEd/7N0xZtI4E3+GR0TIeSe7NW2hZhWilGCpohymJAL+fbOTq1GnZ59I2CMsZdcVg2lE mrevdzJsm7yAr+SQ1DE2oQ==; In-Reply-To: <87zfpbil13.fsf@protonmail.com> (message from Pip Cet on Sat, 17 Aug 2024 08:57:46 +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:322838 Archived-At: > Date: Sat, 17 Aug 2024 08:57:46 +0000 > From: Pip Cet > Cc: emacs-devel@gnu.org > > > Btw, I get the impression that help facilities generate plenty of large > > strings that are ultimately dumped, so it would be useful to measure the > > size of pure space with and without the string deduplication > > optimization enabled, and decide whether it would be worth preserving in > > some form. > > It's already disabled in scratch/igc (when HAVE_MPS is set), and IIRC I > didn't have to increase the pure space size... That's okay, because it isn't "removing pure space", and it is on a feature branch which was not yet landed. So we have enough time to consider what to do with it until it becomes actually relevant. > Keep in mind that the current implementation only works one way: if we > dump "c", then "abc", both strings will be copied to pure space > completely. If we dump "abc", then "c", the second string will be > deduplicated to point at "abc" + 2. I suspect this is the opposite of > what we need. > > So it might be fairer to fix that first, and compare then. However, > once we start implementing rudimentary data compression for dumps, where > do we stop? Once again, the only way towards removing pure space is to decide that we drop support for platforms where Emacs can only be built with unexec. If there's consensus about dropping the unexec-only platforms, we can move towards removing pure; otherwise we cannot.