From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mp2 ([2001:41d0:2:4a6f::]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) by ms11 with LMTPS id cLQGDG/ARGDJBAAA0tVLHw (envelope-from ) for ; Sun, 07 Mar 2021 12:00:47 +0000 Received: from aspmx1.migadu.com ([2001:41d0:2:4a6f::]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) by mp2 with LMTPS id 4NXJB2/ARGDZfAAAB5/wlQ (envelope-from ) for ; Sun, 07 Mar 2021 12:00:47 +0000 Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by aspmx1.migadu.com (Postfix) with ESMTPS id 5A3C21E7A1 for ; Sun, 7 Mar 2021 13:00:46 +0100 (CET) Received: from localhost ([::1]:33234 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lIs5V-0006av-6j for larch@yhetil.org; Sun, 07 Mar 2021 07:00:45 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:37742) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lIs50-0006aW-NM for guix-devel@gnu.org; Sun, 07 Mar 2021 07:00:14 -0500 Received: from mira.cbaines.net ([2a01:7e00:e000:2f8:fd4d:b5c7:13fb:3d27]:36735) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lIs4y-0004Ut-H3 for guix-devel@gnu.org; Sun, 07 Mar 2021 07:00:14 -0500 Received: from localhost (unknown [IPv6:2a02:8010:68c1:0:8ac0:b4c7:f5c8:7caa]) by mira.cbaines.net (Postfix) with ESMTPSA id EEFAA27BC50; Sun, 7 Mar 2021 12:00:06 +0000 (GMT) Received: from capella (localhost [127.0.0.1]) by localhost (OpenSMTPD) with ESMTP id ab6cf970; Sun, 7 Mar 2021 12:00:06 +0000 (UTC) References: <87eegsnexv.fsf@cbaines.net> <87wnujzqyo.fsf@netris.org> User-agent: mu4e 1.4.15; emacs 27.1 From: Christopher Baines To: Mark H Weaver Subject: Re: Implications of QEMU binfmt transparent emulation for builds In-reply-to: <87wnujzqyo.fsf@netris.org> Date: Sun, 07 Mar 2021 12:00:03 +0000 Message-ID: <878s6znph8.fsf@cbaines.net> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha512; protocol="application/pgp-signature" Received-SPF: pass client-ip=2a01:7e00:e000:2f8:fd4d:b5c7:13fb:3d27; envelope-from=mail@cbaines.net; helo=mira.cbaines.net X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: guix-devel@gnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: "Development of GNU Guix and the GNU System distribution." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: guix-devel@gnu.org Errors-To: guix-devel-bounces+larch=yhetil.org@gnu.org Sender: "Guix-devel" X-Migadu-Flow: FLOW_IN ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=yhetil.org; s=key1; t=1615118446; h=from:from:sender:sender: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:list-id:list-help:list-unsubscribe: list-subscribe:list-post; bh=wl84NclpM1gfSREw9w3I+7MmidlBYaFyXsp64V9QPJQ=; b=CG2uIZ8a6vo0to1PTtcv0XEmN4/NWkPqe/H9v2Mi7wFm7E7Qy1cCvhNec+Ib4A0+Wqco67 YEHcXaxMgjaqI+yMd+cbVt7SpC6jlVQ+RdleZgy42pUKTVuGIDbqWyCerAeLdd8T8uSzEH kLw42pdT2MuCk600Rmj6FENzVd+HCYURwSf+6oMHce0V5yC4A3FWyOiqLZ0sjkDgHhXhfM SdiFNf1v8/U+it3wF0Bo4t+bpxqNQ/+f+A2S2wra+jUhQeU41X1CHziy5nyMPwdvlYiEyl CNbRp81uRjaJphgbbik1dqKBAdzCUuBBhAMGl1zusK8IWZtH6xvFR1bkSMw1LA== ARC-Seal: i=1; s=key1; d=yhetil.org; t=1615118446; a=rsa-sha256; cv=none; b=Oys3zob5p4sLJAHU/472/HjzfvZ4Iv1IHHOMu7bu/2O8KEcQDxJhWnTUoopx9j2aF+NFDE DYtughcVHEPH+RtehIXDMQ9XTzqdbK6Yqgkso3WKIXQ7FLljALZJrMR8E3yRHlL5vywpnv mKBFKm8ZOMbZwqZ9E0CSx2N2mVVY+vFnAjLSJuYKnEt2IEZmcvKmvYwbI7f6RxS4Pze5ZH 9D6bf6CxoyW1LfoTwmUOiGUDB6Gw9tNBbTBxSc84DgR6k33pfkdOLhk9Zo8y6YqH4bepuL 8CCHM8c7fO4MwhD17/nshRvYRm3zyjIWJL0fYkXRRZZY/Ab4a5yCTIAp6ckChQ== ARC-Authentication-Results: i=1; aspmx1.migadu.com; dkim=none; dmarc=none; spf=pass (aspmx1.migadu.com: domain of guix-devel-bounces@gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=guix-devel-bounces@gnu.org X-Migadu-Spam-Score: -4.47 Authentication-Results: aspmx1.migadu.com; dkim=none; dmarc=none; spf=pass (aspmx1.migadu.com: domain of guix-devel-bounces@gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=guix-devel-bounces@gnu.org X-Migadu-Queue-Id: 5A3C21E7A1 X-Spam-Score: -4.47 X-Migadu-Scanner: scn1.migadu.com X-TUID: NXgv9GD6pCNl --=-=-= Content-Type: text/plain Mark H Weaver writes: > Hi Christopher, > > Christopher Baines writes: > >> I'm starting to play with mixing native and emulated builds with the >> Guix Build Coordinator again. I did do this many months ago, but at that >> time, there wasn't support for targeting retries across a range of >> machines, to help avoid blockages due to QEMU issues. >> >> Anyway, something that's been on my mind regarding QEMU and builds is >> how well this matches up with building natively. > > Here's one significant problem with emulated builds, although perhaps > not the kind of problem you were asking about: > > Due to differences in the memory models of Intel and other systems such > as ARM, it is easy to write multithreaded code that works robustly on > Intel systems but sporadically fails on other architectures such as ARM. > > However, an ARM emulator running on an Intel system will effectively use > an Intel memory model, because it would be prohibitively expensive to > faithfully simulate the ARM memory model on Intel hardware, and the only > benefit would be to demonstrate bugs that can't happen on Intel systems. > > Therefore, test suites run under an emulator will almost certainly fail > to find architecture-specific thread safety problems, which I expect are > among the most important tests to be done, and among the most likely to > otherwise go unnoticed. > > For this reason, I suggest that we should avoid emulated builds in our > build farm. This is exactly the kind of problem I'm interested in, so thanks for the description. --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQKlBAEBCgCPFiEEPonu50WOcg2XVOCyXiijOwuE9XcFAmBEwENfFIAAAAAALgAo aXNzdWVyLWZwckBub3RhdGlvbnMub3BlbnBncC5maWZ0aGhvcnNlbWFuLm5ldDNF ODlFRUU3NDU4RTcyMEQ5NzU0RTBCMjVFMjhBMzNCMEI4NEY1NzcRHG1haWxAY2Jh aW5lcy5uZXQACgkQXiijOwuE9Xe2vxAAuJZ1pjRpD50YTr3FykgvscOel8CQpfdV aMWVS3aMCL2U/Rs0tG8j6QsWHhFcMJsPDopPE/NJT2qe0uSSOQk2TNrsrifd9QVC nDM41OZq0f9WymAmrn5VSdvF52ysswxLFMpmiPF7b+Nn9cErH/VhZei1bx6IpHpG +fFmcNxxk2EX+qRGXWf9acb9tWqpvaRcKf9BCmjgPlapo6KZ176+gV7HRUJijaQz dsAwBEk1jp0DQYlyZk9JinR1D9naWaWCsL2RB5jgGnKrPobGXTp2TRlQU9xSTbIN FWcjtXRh1fODFVAptIfNt4xKZR7C8HfMvsw02sGFe9/7sS7c5KlvOUNa1M3zSd6P IeOyt6PD64I+dJYBSp8lllR1wc5oqJdnhOSmIDS2nvGiRgGsX+mXwmkGfPlpeutS 0e9sOJFORRx0B0ob+adN1zL/2oABFegcfp7Dep6BJqiPM7SjWt5V/XflhpjYAplR QVitqJsEDORosf0nxlZC/wVugHRzthv5bLMOknFUDL2ZDsOZHyv95rMy3WGM/nqw K/I7iEVt+iTlixZxUDrI2Lq+NgT/XkQx/eW8e6T+owUFeriRdlc/HP69xyXwUOT6 uSLoLUHHI1DDQVneShb7yn6WTHtjLbps6+vXxEfRW9Qi0DoUxlg4Y1qiBKg6DjdE eYdQYnohIoc= =mQAF -----END PGP SIGNATURE----- --=-=-=--