From owner-freebsd-geom@freebsd.org Mon Feb 8 19:01:22 2021 Return-Path: Delivered-To: freebsd-geom@mailman.nyi.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.nyi.freebsd.org (Postfix) with ESMTP id 48DA653D7D3 for ; Mon, 8 Feb 2021 19:01:22 +0000 (UTC) (envelope-from paul@gromit.dlib.vt.edu) Received: from gromit.dlib.vt.edu (gromit.dlib.vt.edu [128.173.49.70]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256 client-signature RSA-PSS (2048 bits) client-digest SHA256) (Client CN "gromit.dlib.vt.edu", Issuer "Chumby Certificate Authority" (not verified)) by mx1.freebsd.org (Postfix) with ESMTPS id 4DZFjs2Wqqz4gBD for ; Mon, 8 Feb 2021 19:01:21 +0000 (UTC) (envelope-from paul@gromit.dlib.vt.edu) Received: from mather.gromit23.net (unknown [73.99.214.146]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by gromit.dlib.vt.edu (Postfix) with ESMTPSA id 6EB2514A; Mon, 8 Feb 2021 14:01:20 -0500 (EST) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Mac OS X Mail 14.0 \(3654.60.0.2.21\)) Subject: Re: Making gmirror metadata cooperate with gpt metadata From: Paul Mather In-Reply-To: Date: Mon, 8 Feb 2021 14:01:19 -0500 Cc: freebsd-geom@freebsd.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <5E7EFDC6-0089-4D6C-B81C-3D98A04C0FA7@gromit.dlib.vt.edu> <4AB2335F-706F-489D-9228-FEECFDD3CC45@gromit.dlib.vt.edu> To: "Kevin P. Neal" X-Mailer: Apple Mail (2.3654.60.0.2.21) X-Rspamd-Queue-Id: 4DZFjs2Wqqz4gBD X-Spamd-Bar: -- Authentication-Results: mx1.freebsd.org; dkim=none; dmarc=fail reason="No valid SPF, No valid DKIM" header.from=vt.edu (policy=none); spf=none (mx1.freebsd.org: domain of paul@gromit.dlib.vt.edu has no SPF policy when checking 128.173.49.70) smtp.mailfrom=paul@gromit.dlib.vt.edu X-Spamd-Result: default: False [-2.50 / 15.00]; RCVD_TLS_ALL(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; FREEFALL_USER(0.00)[paul]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; MV_CASE(0.50)[]; MID_RHS_MATCH_FROM(0.00)[]; MIME_GOOD(-0.10)[text/plain]; ARC_NA(0.00)[]; SPAMHAUS_ZRD(0.00)[128.173.49.70:from:127.0.2.255]; RECEIVED_SPAMHAUS_PBL(0.00)[73.99.214.146:received]; TO_MATCH_ENVRCPT_SOME(0.00)[]; RBL_DBL_DONT_QUERY_IPS(0.00)[128.173.49.70:from]; NEURAL_HAM_LONG(-1.00)[-1.000]; RCPT_COUNT_TWO(0.00)[2]; NEURAL_HAM_SHORT(-1.00)[-1.000]; NEURAL_HAM_MEDIUM(-1.00)[-1.000]; R_SPF_NA(0.00)[no SPF record]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:1312, ipnet:128.173.0.0/16, country:US]; RCVD_COUNT_TWO(0.00)[2]; MAILMAN_DEST(0.00)[freebsd-geom]; DMARC_POLICY_SOFTFAIL(0.10)[vt.edu : No valid SPF, No valid DKIM,none] X-BeenThere: freebsd-geom@freebsd.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: GEOM-specific discussions and implementations List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 08 Feb 2021 19:01:22 -0000 On Feb 8, 2021, at 1:36 PM, Kevin P. Neal wrote: > On Sun, Feb 07, 2021 at 05:55:58PM -0500, Paul Mather wrote: >> To be honest, I don't remember what it does because I only use = gmirror >> for swap nowadays, but I have a sneaking suspicion from memory that = it was >=20 > Is this safe? I thought that gmirror could attempt to allocate memory, = so in > a low memory situation where you are swapping it could deadlock. Actually, I always remember the flipside: there was a time when folks = said not to swap to ZFS volumes because memory pressure from ARC could = lead to increased paging out to swap that could lead to the sort of = deadlock you mention due to even more memory pressure by ZFS. I can't remember hearing any caveats about swapping to gmirror. > Or did that only apply when using encryption? I've never had an issue swapping to a gmirror'd swap partion, encrypted = or otherwise. I build my own packages via Poudriere, which usually = guarantees giving swap a good workout. :-) Cheers, Paul.=