From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id CD634CA9EAE for ; Tue, 29 Oct 2019 08:52:36 +0000 (UTC) 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 mail.kernel.org (Postfix) with ESMTPS id 97F2920663 for ; Tue, 29 Oct 2019 08:52:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="TLMXUMpN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 97F2920663 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:52952 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iPNEx-0007SP-Jt for qemu-devel@archiver.kernel.org; Tue, 29 Oct 2019 04:52:35 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43230) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1iPNDZ-0006GX-Og for qemu-devel@nongnu.org; Tue, 29 Oct 2019 04:51:11 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1iPNDW-00087J-W3 for qemu-devel@nongnu.org; Tue, 29 Oct 2019 04:51:08 -0400 Received: from us-smtp-delivery-1.mimecast.com ([207.211.31.120]:22919 helo=us-smtp-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1iPNDW-00086t-Q8 for qemu-devel@nongnu.org; Tue, 29 Oct 2019 04:51:06 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1572339066; h=from:from: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:autocrypt:autocrypt; bh=qwbfk7oJEcfwd5S9gIDlQfDjvLwLYMJy3QF/hxKVX4E=; b=TLMXUMpNTZg0elCi15mg66tXuLe1IArfdl93co2gAhxpeqqRqDYIW7e17UcGuALXV5lqmS S5V9pfxao29CPbo9aUwPUrXKaBa0CFTGK+ySr4EKF//8hPtLxb/0uaCCQ8+Ab6y+wspQZv RXCa7BFHlEb7Po/LRD/0BvTR00ILh6s= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-77-tl1Ataw3P8KcaW0kSkZw8Q-1; Tue, 29 Oct 2019 04:50:58 -0400 X-MC-Unique: tl1Ataw3P8KcaW0kSkZw8Q-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id A1038800C80; Tue, 29 Oct 2019 08:50:57 +0000 (UTC) Received: from dresden.str.redhat.com (ovpn-116-124.ams2.redhat.com [10.36.116.124]) by smtp.corp.redhat.com (Postfix) with ESMTPS id A732260863; Tue, 29 Oct 2019 08:50:52 +0000 (UTC) Subject: Re: [RFC 0/3] block/file-posix: Work around XFS bug To: Vladimir Sementsov-Ogievskiy , Kevin Wolf , Stefan Hajnoczi References: <20191025095849.25283-1-mreitz@redhat.com> <20191027123555.GN4472@stefanha-x1.localdomain> <20191028110408.GB3579@localhost.localdomain> <44565375-b051-e782-4988-c3e0b1745e37@virtuozzo.com> From: Max Reitz Autocrypt: addr=mreitz@redhat.com; prefer-encrypt=mutual; keydata= mQENBFXOJlcBCADEyyhOTsoa/2ujoTRAJj4MKA21dkxxELVj3cuILpLTmtachWj7QW+TVG8U /PsMCFbpwsQR7oEy8eHHZwuGQsNpEtNC2G/L8Yka0BIBzv7dEgrPzIu+W3anZXQW4702+uES U29G8TP/NGfXRRHGlbBIH9KNUnOSUD2vRtpOLXkWsV5CN6vQFYgQfFvmp5ZpPeUe6xNplu8V mcTw8OSEDW/ZnxJc8TekCKZSpdzYoxfzjm7xGmZqB18VFwgJZlIibt1HE0EB4w5GsD7x5ekh awIe3RwoZgZDLQMdOitJ1tUc8aqaxvgA4tz6J6st8D8pS//m1gAoYJWGwwIVj1DjTYLtABEB AAG0HU1heCBSZWl0eiA8bXJlaXR6QHJlZGhhdC5jb20+iQFTBBMBCAA9AhsDBQkSzAMABQsJ CAcCBhUICQoLAgQWAgMBAh4BAheABQJVzie5FRhoa3A6Ly9rZXlzLmdudXBnLm5ldAAKCRD0 B9sAYdXPQDcIB/9uNkbYEex1rHKz3mr12uxYMwLOOFY9fstP5aoVJQ1nWQVB6m2cfKGdcRe1 2/nFaHSNAzT0NnKz2MjhZVmcrpyd2Gp2QyISCfb1FbT82GMtXFj1wiHmPb3CixYmWGQUUh+I AvUqsevLA+WihgBUyaJq/vuDVM1/K9Un+w+Tz5vpeMidlIsTYhcsMhn0L9wlCjoucljvbDy/ 8C9L2DUdgi3XTa0ORKeflUhdL4gucWoAMrKX2nmPjBMKLgU7WLBc8AtV+84b9OWFML6NEyo4 4cP7cM/07VlJK53pqNg5cHtnWwjHcbpGkQvx6RUx6F1My3y52vM24rNUA3+ligVEgPYBuQEN BFXOJlcBCADAmcVUNTWT6yLWQHvxZ0o47KCP8OcLqD+67T0RCe6d0LP8GsWtrJdeDIQk+T+F xO7DolQPS6iQ6Ak2/lJaPX8L0BkEAiMuLCKFU6Bn3lFOkrQeKp3u05wCSV1iKnhg0UPji9V2 W5eNfy8F4ZQHpeGUGy+liGXlxqkeRVhLyevUqfU0WgNqAJpfhHSGpBgihUupmyUg7lfUPeRM DzAN1pIqoFuxnN+BRHdAecpsLcbR8sQddXmDg9BpSKozO/JyBmaS1RlquI8HERQoe6EynJhd 64aICHDfj61rp+/0jTIcevxIIAzW70IadoS/y3DVIkuhncgDBvGbF3aBtjrJVP+5ABEBAAGJ ASUEGAEIAA8FAlXOJlcCGwwFCRLMAwAACgkQ9AfbAGHVz0CbFwf9F/PXxQR9i4N0iipISYjU sxVdjJOM2TMut+ZZcQ6NSMvhZ0ogQxJ+iEQ5OjnIputKvPVd5U7WRh+4lF1lB/NQGrGZQ1ic alkj6ocscQyFwfib+xIe9w8TG1CVGkII7+TbS5pXHRxZH1niaRpoi/hYtgzkuOPp35jJyqT/ /ELbqQTDAWcqtJhzxKLE/ugcOMK520dJDeb6x2xVES+S5LXby0D4juZlvUj+1fwZu+7Io5+B bkhSVPb/QdOVTpnz7zWNyNw+OONo1aBUKkhq2UIByYXgORPFnbfMY7QWHcjpBVw9MgC4tGeF R4bv+1nAMMxKmb5VvQCExr0eFhJUAHAhVg== Message-ID: <9780d020-e573-866f-dce4-d99d73f1f5e8@redhat.com> Date: Tue, 29 Oct 2019 09:50:50 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 MIME-Version: 1.0 In-Reply-To: <44565375-b051-e782-4988-c3e0b1745e37@virtuozzo.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="2XHFDAcRiRzgTFkjV70vYlClaTzCIIPRP" X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Anton Nefedov , Alberto Garcia , "qemu-devel@nongnu.org" , "qemu-block@nongnu.org" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --2XHFDAcRiRzgTFkjV70vYlClaTzCIIPRP Content-Type: multipart/mixed; boundary="nyFGOSYrHPEsqQ22rTN9NK5QJLRx54G1Y" --nyFGOSYrHPEsqQ22rTN9NK5QJLRx54G1Y Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 28.10.19 12:25, Vladimir Sementsov-Ogievskiy wrote: > 28.10.2019 14:04, Kevin Wolf wrote: >> Am 27.10.2019 um 13:35 hat Stefan Hajnoczi geschrieben: >>> On Fri, Oct 25, 2019 at 11:58:46AM +0200, Max Reitz wrote: [...] >>>> (3) Drop handle_alloc_space(), i.e. revert c8bb23cbdbe32f. >>>> To my knowledge I=E2=80=99m the only one who has provided any ben= chmarks for >>>> this commit, and even then I was a bit skeptical because it perfo= rms >>>> well in some cases and bad in others. I concluded that it=E2=80= =99s >>>> probably worth it because the =E2=80=9Csome cases=E2=80=9D are mo= re likely to occur. >>>> >>>> Now we have this problem of corruption here (granted due to a bug= in >>>> the XFS driver), and another report of massively degraded >>>> performance on ppc64 >>>> (https://bugzilla.redhat.com/show_bug.cgi?id=3D1745823 =E2=80=93 = sorry, a >>>> private BZ; I hate that :-/ The report is about 40 % worse >>>> performance for an in-guest fio write benchmark.) >>>> >>>> So I have to ask the question about what the justification for >>>> keeping c8bb23cbdbe32f is. How much does performance increase wi= th >>>> it actually? (On non-(ppc64+XFS) machines, obviously) >>>> >>>> Advantages: >>>> + Trivial >>>> + No layering violations >>>> + We wouldn=E2=80=99t need to keep track of whether the kernel bu= g has been >>>> fixed or not >>>> + Fixes the ppc64+XFS performance problem >>>> >>>> Disadvantages: >>>> - Reverts cluster allocation performance to pre-c8bb23cbdbe32f >>>> levels, whatever that means >>> >>> My favorite because it is clean and simple, but Vladimir has a valid >>> use-case for requiring this performance optimization so reverting isn't >>> an option. >> >> Vladimir also said that qcow2 subclusters would probably also solve his >> problem, so maybe reverting and applying the subcluster patches instead >> is a possible solution, too? >=20 > I'm not sure about ssd case, it may need write-zero optimization anyway. What exactly do you need? Do you actually need to write zeroes (e.g. because you=E2=80=99re storing images on block devices) or would it be sufficient to just drop the COW areas when bdrv_has_zero_init() and bdrv_has_zero_init_truncate() are true? I=E2=80=99m asking because Dave Chinner said (https://bugzilla.redhat.com/show_bug.cgi?id=3D1765547#c7) that fallocate() is always slow at least with aio=3Dnative because it needs to wait for all concurrent AIO writes to finish, and so it causes the AIO pipeline to stall. (He suggested using XFS extent size hints to get the same effect as write-zeroes for free, basically, but I don=E2=80=99t know whether that=E2= =80=99s really useful to us; as unallocated areas on XFS read back as zero anyway.) >> We already have some cases where the existing handle_alloc_space() >> causes performance to actually become worse, and serialising requests as >> a workaround isn't going to make performance any better. So even on >> these grounds, keeping commit c8bb23cbdbe32f is questionable. >> >=20 > Can keeping handle_alloc_space under some config option be an option? Hm. A config option is weird if you=E2=80=99re the only one who=E2=80=99s = going to enable it. But other than that I don=E2=80=99t have anything against it. Max --nyFGOSYrHPEsqQ22rTN9NK5QJLRx54G1Y-- --2XHFDAcRiRzgTFkjV70vYlClaTzCIIPRP Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEkb62CjDbPohX0Rgp9AfbAGHVz0AFAl23/WoACgkQ9AfbAGHV z0C8LwgAtLkCIFZnozIb+uTr8niqqEMJx3NWA89w5IdGxdjXApTN8UIVrMvsXT+N fgfuq0lJCZ9MIL+WpunAW8R3RDKsKf/HrDiAg/RDpcMsBnA2qyBY6DmWSTo6tuFn Kx3/IXprshLNxsO9QItRFhaS+8zqV8PsUjBTPjOZaLJtSonnldJrh6aauFdaa17M Jvd1xbKv3YOypfPKKGjYHjo0A7IkQrlw8kRN7z9pnNifdhTG6b+gveDgVtYsdxWW vTrOXD2Ugx0M2vLtPBZDdbxZ0TlIdsu301mhLsKSplizBe/x5O7PN6vJBr2VyYiU YlzG+Nl5izTZriLxbRF1SRlgOv6EMw== =v7Om -----END PGP SIGNATURE----- --2XHFDAcRiRzgTFkjV70vYlClaTzCIIPRP--